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  • 1.
    Anaby, Dana
    et al.
    School of Physical and Occupational Therapy, McGill University, Montreal, Canada.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Kroksmark, Ulla
    Sahlgrenska Academy, Institute of Neuroscience and Physiology, University of Gothenburg, Göteburg, Sweden.
    Ellegård, Kajsa
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Changes in participation patterns of youth with physical disabilities following the Pathways and Resources for Engagement and Participation intervention: A time-geography approach2019Ingår i: Scandinavian Journal of Occupational Therapy, ISSN 1103-8128, E-ISSN 1651-2014Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: The PREP (Pathways and Resources for Engagement and Participation), an innovative 12-week occupational therapy intervention that focuses on changing the environment, was found effective in improving the participation of youth in specific chosen community-based activities.

    Objective: To complement existing evidence, this study explored changes in overall participation patterns of youth with physical disabilities following the PREP intervention.

    Methods: Guided by time-geography approach, 13 youth aged 12–17 completed a 24-hr diary using the Aday app during one typical weekday and another day during the weekend, pre- and post-intervention. Data of 50 diaries were plotted and analyzed using the VISUALTimePAcTS program.

    Results: Following the PREP, youth were engaged in less digital media and more in study-related activities. Number of occurrences and time spent doing activities with friends were greater post-intervention, whereas time spent doing activities at home was quite similar, particularly during the weekdays. During the weekends, however, youth spent slightly less time at home.

    Conclusions and significance: Findings provide preliminary support for the effectiveness of the PREP, extending beyond the accomplishment of specific targeted activities towards a change in the overall daily patterns of youth. Such knowledge can redirect occupational therapists’ attention to environment-focused interventions involving real-life experiences.

  • 2.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Rydergren, Clas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Rajna, Botond
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Carlsson, Richard
    Ericsson Research, Services & Software.
    Forgeat, Julien
    Ericsson Research, Services & Software.
    Hu, Tracy H
    Ericsson Research, Services & Software.
    Liu, Evan L
    Ericsson Research, Services & Software.
    Moritz, Simon
    Ericsson Research, Services & Software.
    Zhao, Sky
    Ericsson Research, Services & Software.
    Zheng, Yaotian
    Ericsson Research, Services & Software.
    Mobility modeling for transport efficiency: Analysis of travel characteristics based on mobile phone data2013Ingår i: Netmob 2013: Mobile phone data for development / [ed] Vincent Blondel, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Signaling data from the cellular networks can provide a means of analyzing the efficiency of a deployed transportation system and assisting in the formulation of transport models to predict its future use. An approach based on this type of data can be especially appealing for transportation systems that need massive expansions, since it has the added benefit that no specialized equipment or installations are required, hence it can be very cost efficient.

    Within this context in this paper we describe how such obtained data can be processed and used in order to act as enablers for traditional transportation analysis models. We outline a layered, modular architectural framework that encompasses the entire process and present results from initial analysis of mobile phone call data in the context of mobility, transport and transport infrastructure. We finally introduce the Mobility Analytics Platform, developed by Ericsson Research, tailored for mobility analysis, and discuss techniques for analyzing transport supply and demand, and give indication on how cell phone use data can be used directly to analyze the status and use of the current transport infrastructure.

  • 3.
    Ceccato, Vania
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Urbana och regionala studier..
    Wiebe, Douglas J
    University of Pennsylvania, Philadelphia, USA.
    Eshraghi, Bita
    Karolinska Institute, Stockholm, Sweden.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Women’s Mobility and the Situational Conditions of Rape: Cases Reported to Hospitals2017Ingår i: Journal of Interpersonal Violence, ISSN 0886-2605, E-ISSN 1552-6518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A third of all rapes in Stockholm, the capital of Sweden, take place in public outdoor places. Yet, little is known about the events that precede this type of sexual offence and less about the situational context of rape. This study aims to improve the understanding of the nature of situational conditions that immediately precede events of rape. Using medical records of 147 rape victims during 2012 and 2013, we constructed time- and place-specific records of the places women traveled through or spent time at, the activities they engaged in, and the people they interacted with sequentially over the course of the day when they were raped. The analysis uses visualization tools (VISUAL-TimePAcTS), Geographical Information Systems, and conditional logistic regression to identify place-, context-, and social interaction–related factors associated with the onset of rape. Results for this sample of cases reported to hospitals show that being outdoors was not necessarily riskier for women when compared with indoor public settings; some outdoor environments were actually protective, such as streets. Being in a risky social context and engaging in a risky activity before the event was associated with an increased risk of rape, and the risk escalated over the day. Among those women who never drank alcohol, the results were similar to what was observed in the overall sample, which suggests that risky social interaction and risky activity made independent contributions to the risk of rape. The article finishes with suggestions for rape prevention.

  • 4.
    Ellegård, Kajsa
    et al.
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Capturing patterns of everyday life: presentation of the visualization method VISUAL-TimePAcTS2006Ingår i: International Association for Time Use Research Annual Conference, Copenhagen, Denmark: Danish National Institute of Social Research , 2006Konferensbidrag (Refereegranskat)
  • 5.
    Ellegård, Kajsa
    et al.
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    En tidsgeografisk studie av strukturen i lärares vardag2013Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Rapporten En tidsgeografisk studie av lärares vardag bygger på det dagboksmaterial som Skolverket samlade in under våren 2012 från drygt 3 600 lärare. Den besvarar frågor som:

    • När under dagen utförs arbetsrelaterade aktiviteter och var utförs de?
    • Har aktiviteterna lång eller kort varaktighet?
    • Vilka skillnader och likheter finns mellan lärare i olika årskurser? V
    • ilka arbetsrelaterade aktiviteter utförs efter lektionstid och var genomförs de?
    • Finns det sekvenser av aktiviteter som återkommer hos många lärare i yrkesvardagen?

    I rapporten visualiseras grundskollärares tidsanvändning så att deras aktiviteter under dygnet beskrivs i den tidsordning som de genomförs.

    Resultatet visar att lärares arbetsvecka i mångt och mycket ser likartad ut. Det tar sig uttryck i att lärare arbetar ungefär lika långa dagar, vistas ungefär lika lång tid i skolan, genomför till viss del samma aktivitetssekvenser. De flesta arbetsrelaterade aktiviteterna genomförs i skolan, men många lärare utför också arbetsrelaterade aktiviteter på kvällstid i hemmet. Påtagliga skillnader framgår mellan veckans fyra första dagar och fredagar och mellan lärare i olika årskurser i flera olika avseenden.

    Lärares yrkesvardag analyseras med hjälp av de tidsgeografiska begreppen projekt och restriktioner. Lärares förvärvsarbete är ett individprojekt och detta ska passa in både i skolans organisationsprojekt (med målet att skapa förutsättningar för elevernas lärande) och i det egna hushållets organisationsprojekt (med målet att skapa ett bra liv för hushållsmedlemmarna).

    Skolans organisationsprojekt innebär auktoritetsrestriktioner för lärare genom att de måste följa avtal, arbeta enligt bestämda undervisningsscheman och delta i föreskrivna möten. För lärarnas del innebär bland annat schemaläggningen av undervisningen att kopplingsrestriktioner uppstår. Lärare som vill eller behöver arbeta tillsammans måste ha tidsmässiga möjligheter och någon ledig lokal för att genomföra sina gemensamma aktiviteter och då kan inte någon av dem vara schemalagd för lektioner. Kopplingsrestriktioner uppträder t ex när tätt packade scheman och högt tryck på skolans lokaler och försvårar för samarbete mellan lärare.

    När arbetsrelaterade aktiviteter utförs hemma på kvällstid vävs skolans organisationsprojekt in i lärarhushållets privata projekt. Det innebär att lärares individprojekt förvärvsarbete blir en kopplingsrestriktion som hindrar henne/honom från att samtidigt delta i hushållets privata projekt. Kanske skulle t ex utökad tillgång till arbetsutrymmen i skolan där aktiviteter kan utföras ostört och koncentrerat, möjliggöra för lärare att genomföra mer av sina arbetsrelaterade aktiviteter på dagtid och i skolan?

    Visualiseringen av den kontextuella tidsanvändningen och analysen av de kopplingsrestriktioner som uppstår i lärarnas yrkesvardag indikerar att andra former av organisering av en del arbetsrelaterade aktiviteterna skulle kunna frigöra tid för lärarnas kärnaktiviteter.

  • 6.
    Ellegård, Kajsa
    et al.
    Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Institutionen för tema, Tema teknik och social förändring.
    Vrotsou, Katerina
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik.
    Widén, Joakim
    Department of engineering science, Uppsala University.
    VISUAL-TimePAcTS / energy use: a software application for visualizing energy use from activities performed2015Ingår i: Socio-technical perspectives on sustainable energy systems / [ed] Jonas Anshelm, Kajsa Ellegård, Jenny Palm, Harald Rohracher, Linköping: Linköping University , 2015, s. 127-145Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 7.
    Ellegård, Kajsa
    et al.
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Widén, Joakim
    Teknikvetenskaper, fastat illståndets fysik, Uppsala universitet,.
    VISUAL-TimePAcTS/energy use: a soft ware application for visualizing energy use from activities performed2010Ingår i: Conference proceedings 3rd International Scientific Conference on “Energy systems with IT” / [ed] Erik Dahlqvist & Jenny Palm, 2010, s. 1-16Konferensbidrag (Refereegranskat)
    Abstract [en]

    We will present the software application VISUAL-TimePAcTS/energy use. The application shows, in a flexible way, the energy use of individuals, households, groups and whole populations which is calculated through individuals’ performed activities. Input data is diary logs for the 24 hours of the day. There are several visualizations opportunities. First, all activities performed by each individual in the population can be shown. Second, activity patterns (i.e. combinations and repetitions of activities) can be identified and represented. Third, the activities that request energy for their performance can be visualized. Fourth, “load curves” that show the power demand can be constructed, within the application, from a set of rules relating energy consumed by different appliances to performed activities requiring these appliances. We will also present principles used for doing the activity categorization (a categorization scheme), and how we hope to develop the software further. The application opens new opportunities to make use of national time use surveys.

  • 8.
    Ellegård, Kajsa
    et al.
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Widén, Joakim
    Uppsala universitet; Institutionen för teknikvetenskaper; Fasta tillståndets fysik.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Appliances Facilitating Everyday Life - Electricity Use Derived from Daily Activities2011Ingår i: Proceeding from the World Renewable Energy Congress - Sweden, 8-13 May, 2011 / [ed] Bahram Moshfegh, Linköping University Electronic Press , 2011, s. 1031-1038Konferensbidrag (Refereegranskat)
    Abstract [en]

    The purpose of this paper is to present how, using a visualization method, electricity use can be derived from the everyday activity patterns of household members. Target groups are, on the one hand, professionals in the energy sector and energy advisors who need more knowledge about household energy use, and, on the other hand, household members wanting to reduce the energy use by revealing their own habits and thereby finding out how changed activity performance may influence electricity use. The focus is on the relation between utilizing electric appliances to perform everyday life activities and the use of electricity. The visualization method is based on the time-geographic approach developed by Hägerstrand and includes a model that estimates appliance electricity use from household members’ activities. Focus, in this paper, is put on some basic activities performed to satisfy daily life needs: cooking and use of information, communication and entertainment devices. These activities appear frequently in the everyday life of households, even though not all household members perform them all. The method is applied on a data material comprising time-diaries written by 463 individuals (aged 10 to 85+) in 179 households in different parts of Sweden. The visualization method reveals when and for how long activities that claim electric appliances are performed by which individual(s). It also shows electricity load curves generated from the use of appliances at different levels, such as individual, household and group or population levels. At household level the method can reveal which household members are the main users of electricity, i.e. the division of labour between household members. Thereby it also informs about whom could be approached by energy companies and energy advisors in information campaigns. The main result of the study is that systematic differences in activity patterns in subgroups of a population can be identified (e.g. men and women) but that directed information based on these patterns has to be made with care and with the risk of making too broad generalizations.

  • 9.
    Haga, Monika
    et al.
    Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Bredland, Ebba
    Department of Neuromedicine and Movement Science, Norwegian University of Science and Technology, Trondheim, Norway.
    Visualizing Physical Activity Patterns among Community-Dwelling Older Adults: A Pilot Study2018Ingår i: Sports, ISSN 2075-4663, Vol. 6, nr 4, artikel-id 135Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Regular physical activity relates to physical and mental functioning in older people, and promoting physical activity has the potential to substantially reduce functional decline and improve well-being. Despite this, investigations of the physical activity quotient through participation in functional activities in everyday life have traditionally gained limited focus among older populations compared to leisure-time physical activity and exercise. Considering the accumulated evidence of the health benefits of low-intensity physical activity, exploring and measuring such activities in this population is highly relevant. The aim of this study was to visualize and describe older people’s physical activity patterns in daily life using a time-geographic approach in combination with the estimation of metabolic equivalents (METS). To exemplify the new method, a sample of nine retired men (65–82 years old, mean age 76.4 ± 5.8) with no homecare services from the municipality was recruited. In order to enable a visual analysis of the physical activity patterns in daily life, we developed the VISUAL-PA software, which is a visual analysis tool that includes METS to account for intensity and enables the analysis of distinct types and domains of physical activity. The VISUAL-PA software creates graphic outputs of physical activity patterns that enable the identification, visualization, and analysis of distinct types and intensities of physical activity in addition to sedentary behavior. The use of VISUAL-PA can contribute to a broader understanding of the complexity in physical activity patterns among older adults in terms of dimensions such as activity patterns and habits, domains, and intensity level. To strengthen the public health strategies that promote health and an active lifestyle, additional knowledge about physical activity patterns is necessary. Moreover, the visualization of physical activity can enable reflections on and awareness of activity habits and preferences, and thus facilitate behavior changes in older individuals.

  • 10.
    Mattioli, Giulio
    et al.
    University of Leeds, England.
    Anable, Jillian
    University of Leeds, England.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Car dependent practices: Findings from a sequence pattern mining study of UK time use data2016Ingår i: Transportation Research Part A: Policy and Practice, ISSN 0965-8564, E-ISSN 1879-2375, Vol. 89, s. 56-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper identifies three main understandings of the notion of car dependence in transport research: a micro-social understanding (dependence as an attribute of individuals), a macro approach (attribute of societies or local areas as whole), and a meso-level understanding, where it refers to trips - or rather to the activities that people travel to undertake. While the first two approaches have been dominant, this paper further develops the third, addressing questions as to whether and why certain activities are inherently more difficult to switch away from the car. At the theoretical level, it builds on theories of social practice to put forward the notion of car dependent practices. At the empirical level, it demonstrates that the application of sequence pattern mining techniques to time use data allows the identification of car and mobility intensive activities, arguably representing the trace of car dependent practices. Overall, the findings of this mining exercise suggest that the emphasis of existing literature on escorting children, shopping and carrying heavy goods as car dependent trip purposes is not misplaced. Our analysis adds to this knowledge by contextualising the information by providing detailed quantitative analysis of a larger, richer set of activities hitherto overlooked in transport policy. The article concludes by illustrating the policy implications of the approach adopted and the findings generated, discussing possible strategies to steer practices in a more sustainable direction by creating material alternatives to the cargo function of car travel. (C) 2016 The Author(s). Published by Elsevier Ltd.

  • 11.
    Muthumanickam, Prithiviraj
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Forsell, Camilla
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Johansson, Jimmy
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Supporting Exploration of Eye Tracking Data: Identifying Changing Behaviour Over Long Durations2016Ingår i: BEYOND TIME AND ERRORS: NOVEL EVALUATION METHODS FOR VISUALIZATION, BELIV 2016, ASSOC COMPUTING MACHINERY , 2016, s. 70-77Konferensbidrag (Refereegranskat)
    Abstract [en]

    Visual analytics of eye tracking data is a common tool for evaluation studies across diverse fields. In this position paper we propose a novel user-driven interactive data exploration tool for understanding the characteristics of eye gaze movements and the changes in these behaviours over time. Eye tracking experiments generate multidimensional scan path data with sequential information. Many mathematical methods in the past have analysed one or a few of the attributes of the scan path data and derived attributes such as Area of Interest (AoI), statistical measures, geometry, domain specific features etc. In our work we are interested in visual analytics of one of the derived attributes of sequential data-the: AoI and the sequences of visits to these AoIs over time. In the case of static stimuli, such as images, or dynamic stimuli, like videos, having predefined or fixed AoIs is not an efficient way of analysing scan path patterns. The AoI of a user over a stimulus may evolve over time and hence determining the AoIs dynamically through temporal clustering could be a better method for analysing the eye gaze patterns. In this work we primarily focus on the challenges in analysis and visualization of the temporal evolution of AoIs. This paper discusses the existing methods, their shortcomings and scope for improvement by adopting visual analytics methods for event-based temporal data to the analysis of eye tracking data.

  • 12.
    Muthumanickam, Prithiviraj
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Johansson, Jimmy
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Shape Grammar Extraction for Efficient Query-by-Sketch Pattern Matching in Long Time Series2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Long time-series, involving thousands or even millions of time steps, are common in many application domains but remain very difficult to explore interactively. Often the analytical task in such data is to identify specific patterns, but this is a very complex and computationally difficult problem and so focusing the search in order to only identify interesting patterns is a common solution. We propose an efficient method for exploring user-sketched patterns, incorporating the domain expert’s knowledge, in time series data through a shape grammar based approach. The shape grammar is extracted from the time series by considering the data as a combination of basic elementary shapes positioned across different am- plitudes. We represent these basic shapes using a ratio value, perform binning on ratio values and apply a symbolic approximation. Our proposed method for pattern matching is amplitude-, scale- and translation-invariant and, since the pattern search and pattern con- straint relaxation happen at the symbolic level, is very efficient permitting its use in a real-time/online system. We demonstrate the effectiveness of our method in a case study on stock market data although it is applicable to any numeric time series data.

  • 13.
    Muthumanickam, Prithiviraj
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Vitoria, Aida
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Johansson, Jimmy
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för klimatpolitisk forskning, CSPR.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Identification of Temporally Varying Areas of Interest in Long-Duration Eye-Tracking Data Sets2018Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Eye-tracking has become an invaluable tool for the analysis of working practices in many technological fields of activity. Typically studies focus on short tasks and use static expected areas of interest (AoI) in the display to explore subjects’ behaviour, making the analyst’s task quite straightforward. In long-duration studies, where the observations may last several hours over a complete work session, the AoIs may change over time in response to altering workload, emergencies or other variables making the analysis more difficult. This work puts forward a novel method to automatically identify spatial AoIs changing over time through a combination of clustering and cluster merging in the temporal domain. A visual analysis system based on the proposed methods is also presented. Finally, we illustrate our approach within the domain of air traffic control, a complex task sensitive to prevailing conditions over long durations, though it is applicable to other domains such as monitoring of complex systems. 

  • 14.
    Peca, Iulian
    et al.
    University of Bonn and Fraunhofer Institute for Intelligent Analysis and Information Systems (IAIS), Germany.
    Fuchs, Georg
    University of Bonn and Fraunhofer Institute for Intelligent Analysis and Information Systems (IAIS), Germany.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Andrienko, Natalia
    University of Bonn and Fraunhofer Institute for Intelligent Analysis and Information Systems (IAIS), Germany.
    Andrienko, Gennady
    University of Bonn and Fraunhofer Institute for Intelligent Analysis and Information Systems (IAIS), Germany.
    Scalable Cluster Analysis of Spatial Events2012Ingår i: EuroVA 2012: International Workshop on Visual Analytics / [ed] K. Matkovic and G. Santucci, Eurographics - European Association for Computer Graphics, 2012, s. 19-23Konferensbidrag (Refereegranskat)
    Abstract [en]

    Clustering of massive data is an important analysis tool but also challenging since the data often does not fit in RAM. Many clustering algorithms are thus severely memory-bound. This paper proposes a deterministic density clustering algorithm based on DBSCAN that allows to discover arbitrary shaped clusters of spatio-temporal events that (1) achieves scalability to very large datasets not fitting in RAM and (2) exhibits significant execution time improvements for processing the full dataset compared to plain DBSCAN. The proposed algorithm's integration with interactive visualization methods allows for visual inspection of clustering results in the context of the analysis task; several alternatives are discussed by means of an application example about traffic data analysis.

  • 15.
    Vrotsou, Katerina
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Everyday mining: Exploring sequences in event-based data2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Event-based data are encountered daily in many disciplines and are used for various purposes. They are collections of ordered sequences of events where each event has a start time and a duration. Examples of such data include medical records, internet surfing records, transaction records, industrial process or system control records, and activity diary data.

    This thesis is concerned with the exploration of event-based data, and in particular the identification and analysis of sequences within them. Sequences are interesting in this context since they enable the understanding of the evolving character of event data records over time. They can reveal trends, relationships and similarities across the data, allow for comparisons to be made within and between the records, and can also help predict forthcoming events.The presented work has researched methods for identifying and exploring such event-sequences which are based on modern visualization, interaction and data mining techniques.

    An interactive visualization environment that facilitates analysis and exploration of event-based data has been designed and developed, which permits a user to freely explore different aspects of this data and visually identify interesting features and trends. Visual data mining methods have been developed within this environment, that facilitate the automatic identification and exploration of interesting sequences as patterns. The first method makes use of a sequence mining algorithm that identifies sequences of events as patterns, in an iterative fashion, according to certain user-defined constraints. The resulting patterns can then be displayed and interactively explored by the user.The second method has been inspired by web-mining algorithms and the use of graph similarity. A tree-inspired visual exploration environment has been developed that allows a user to systematically and interactively explore interesting event-sequences.Having identified interesting sequences as patterns it becomes interesting to further explore how these are incorporated across the data and classify the records based on the similarities in the way these sequences are manifested within them. In the final method developed in this work, a set of similarity metrics has been identified for characterizing event-sequences, which are then used within a clustering algorithm in order to find similarly behavinggroups. The resulting clusters, as well as attributes of the clusteringparameters and data records, are displayed in a set of linked views allowing the user to interactively explore relationships within these.

    The research has been focused on the exploration of activity diary data for the study of individuals' time-use and has resulted in a powerful research tool facilitating understanding and thorough analysis of the complexity of everyday life.

    Delarbeten
    1. Capturing patterns of everyday life: presentation of the visualization method VISUAL-TimePAcTS
    Öppna denna publikation i ny flik eller fönster >>Capturing patterns of everyday life: presentation of the visualization method VISUAL-TimePAcTS
    2006 (Engelska)Ingår i: International Association for Time Use Research Annual Conference, Copenhagen, Denmark: Danish National Institute of Social Research , 2006Konferensbidrag, Publicerat paper (Refereegranskat)
    Ort, förlag, år, upplaga, sidor
    Copenhagen, Denmark: Danish National Institute of Social Research, 2006
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-35802 (URN)28606 (Lokalt ID)28606 (Arkivnummer)28606 (OAI)
    Konferens
    International Association for Time-Use Research Conference, Copenhagen, Denmark
    Anmärkning
    CD proceedings hence no page numbers.Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2015-06-02
    2. 2D and 3D Representations for Feature Recognition in Time Geographical Diary Data
    Öppna denna publikation i ny flik eller fönster >>2D and 3D Representations for Feature Recognition in Time Geographical Diary Data
    2010 (Engelska)Ingår i: Information Visualization, ISSN 1473-8716, E-ISSN 1473-8724, Vol. 9, nr 4, s. 263-276Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Time geographical representations are becoming a common approach to analysing spatio-temporal data. Such representations appear intuitive in the process of identifying patterns and features as paths of populations form tracks through the 3D space, which can be seen converging and diverging over time. In this article, we compare 2D and 3D representations within a time geographical visual analysis tool for activity diary data. We identify a representative task and evaluate task performance between the two representations. The results show that the 3D representation has benefits over the 2D representation for feature identification but also indicate that these benefits can be lost if the 3D representation is not carefully constructed to help the user to see them.

    Ort, förlag, år, upplaga, sidor
    Palgrave Macmillan Ltd, 2010
    Nyckelord
    evaluation, 2D and 3D representation, time geography, time cube, time diary data
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-52360 (URN)10.1057/ivs.2009.30 (DOI)000284461700004 ()
    Tillgänglig från: 2009-12-17 Skapad: 2009-12-17 Senast uppdaterad: 2017-12-12
    3. Everyday Life Discoveries: Mining and Visualizing Activity Patterns in Social Science Diary Data
    Öppna denna publikation i ny flik eller fönster >>Everyday Life Discoveries: Mining and Visualizing Activity Patterns in Social Science Diary Data
    2007 (Engelska)Ingår i: IEEE International Conference on Information Visualisation,2007: ISSN 1550-6037 / [ed] Ebad Banissi, Remo Aslak Burkhard, Georges Grinstein, Urska Cvek, Marjan Trutschl, Liz Stuart, Theodor G Wyeld, Gennady Andrienko, Jason Dykes, Mikael Jern, Dennis Groth and Anna Ursyn, Los Alamitos, CA, USA: IEEE , 2007, s. 130-138Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The ability to identify and examine patterns of activities is a key tool for social and behavioural science. In the past this has been done by statistical or purely visual methods but automated sequential pattern analysis through sophisticated data mining and visualization tools for pattern location and evaluation can open up new possibilities for interactive exploration of the data. This paper describes the addition of a sequential pattern identification method to the visual activity-analysis tool, VISUAL-TimePAcTS, and its effectiveness in the process of pattern analysis in social science diary data. The results have shown that the method correctly identifies patterns and conveys them effectively to the social scientist in a manner that allows them quick and easy understanding of the significance of the patterns.

    Ort, förlag, år, upplaga, sidor
    Los Alamitos, CA, USA: IEEE, 2007
    Serie
    Information Visualization, ISSN 1550-6037
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-40111 (URN)10.1109/IV.2007.48 (DOI)52273 (Lokalt ID)0-7695-2900-3 (ISBN)52273 (Arkivnummer)52273 (OAI)
    Konferens
    11th International Conference in Information Visualization, 4-6 July, Zürich, Switzerland
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2015-06-02Bibliografiskt granskad
    4. Exploring time diaries using semi-automated activity pattern extraction
    Öppna denna publikation i ny flik eller fönster >>Exploring time diaries using semi-automated activity pattern extraction
    2009 (Engelska)Ingår i: electronic International Journal of Time Use Research (eIJTUR), Vol. 6, nr 1, s. 1-25Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Identifying patterns of activities in time diaries in order to understand the variety of daily life in terms of combinationsof activities performed by individuals in different groups is of interest in time use research. So far, activitypatterns have mostly been identified by visually inspecting representations of activity data or by using sequencecomparison methods, such as sequence alignment, in order to cluster similar data and then extract representativepatterns from these clusters. Both these methods are sensitive to data size, pure visual methods becometoo cluttered and sequence comparison methods become too time consuming. Furthermore, the patterns identifiedby both methods represent mostly general trends of activity in a population, while detail and unexpectedfeatures hidden in the data are often never revealed. We have implemented an algorithm that searches the timediaries and automatically extracts all activity patterns meeting user-defined criteria of what constitutes a validpattern of interest for the user’s research question. Amongst the many criteria which can be applied are a timewindow containing the pattern, minimum and maximum occurrences of the pattern, and number of people thatperform it. The extracted activity patterns can then be interactively filtered, visualized and analyzed to revealinteresting insights. Exploration of the results of each pattern search may result in new hypotheses which can besubsequently explored by altering the search criteria. To demonstrate the value of the presented approach weconsider and discuss sequential activity patterns at a population level, from a single day perspective.

    Nyckelord
    Time-geography, diaries, everyday life, activity patterns, visualization, data mining, sequential pattern mining
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-51231 (URN)
    Tillgänglig från: 2009-10-22 Skapad: 2009-10-22 Senast uppdaterad: 2015-03-20
    5. Seeing Beyond Statistics: Visual Exploration of Productivity on a Construction Site
    Öppna denna publikation i ny flik eller fönster >>Seeing Beyond Statistics: Visual Exploration of Productivity on a Construction Site
    2008 (Engelska)Ingår i: Vis 2008, Visualisation: Visualisation in Built and Rural Enviroments, Los Alamitos, CA, USA: IEEE Computer Society, 2008, s. 37-42Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Work on the construction site is known to be inefficient due to workers spending much time waiting for materials, transporting materials and from frequent interruptions of tasks. Studies on the construction site typically use statistical measures to analyse the sampled data about work and such measures, while very useful, can overlook important features of the data. In this paper we apply a previously developed approach, derived from Time Geographical methods, to visually represent the sampled construction productivity data and show that this method may enable the analyst to better understand the distribution of activities, and how they are interrelated and dependent upon each other. 

    Ort, förlag, år, upplaga, sidor
    Los Alamitos, CA, USA: IEEE Computer Society, 2008
    Nyckelord
    construction productivity, visual exploration, visualization, work sampling
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-43044 (URN)10.1109/VIS.2008.27 (DOI)000258052600006 ()71159 (Lokalt ID)978-0-7695-3271-4 (ISBN)71159 (Arkivnummer)71159 (OAI)
    Konferens
    International Conference Visualisation (VIS 2008), London, UK, 9-11 July 2008
    Tillgänglig från: 2009-10-10 Skapad: 2009-10-10 Senast uppdaterad: 2015-09-22Bibliografiskt granskad
    6. ActiviTree: Interactive Visual Exploration of Sequences in Event-Based Data Using Graph Similarity
    Öppna denna publikation i ny flik eller fönster >>ActiviTree: Interactive Visual Exploration of Sequences in Event-Based Data Using Graph Similarity
    2009 (Engelska)Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, ISSN 1077-2626, Vol. 15, nr 6, s. 945-952Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The identification of significant sequences in large and complex event-based temporal data is a challenging problem with applications in many areas of todays information intensive society. Pure visual representations can be used for the analysis, but are constrained to small data sets. Algorithmic search mechanisms used for larger data sets become expensive as the data size increases and typically focus on frequency of occurrence to reduce the computational complexity, often overlooking important infrequent sequences and outliers. In this paper we introduce an interactive visual data mining approach based on an adaptation of techniques developed for web searching, combined with an intuitive visual interface, to facilitate user-centred exploration of the data and identification of sequences significant to that user. The search algorithm used in the exploration executes in negligible time, even for large data, and so no pre-processing of the selected data is required, making this a completely interactive experience for the user. Our particular application area is social science diary data but the technique is applicable across many other disciplines.

    Nyckelord
    Interactive visual exploration, event-based data, sequence identification, graph similarity, node similarity
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-51476 (URN)10.1109/TVCG.2009.117 (DOI)
    Tillgänglig från: 2009-11-04 Skapad: 2009-11-04 Senast uppdaterad: 2017-12-12
    7. Behaviour-driven clustering based on event-sequence similarity metrics
    Öppna denna publikation i ny flik eller fönster >>Behaviour-driven clustering based on event-sequence similarity metrics
    2010 (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    When analysing event data two key objectives are to first identify interesting subsequences in the data records and then to retrieve groups of records that exhibit similar behaviour. This is especially true when the focus of the exploration is the human, for example when using activity diaries to reveal sub-populations with similar behaviour, medical records to identify groups with similar medical conditions, or web sessions to find groups with similar web-surfing habits. In this paper we propose a visual exploration approach, based on sequence similarity metrics and clustering techniques, that will allow an analyst to interactively explore the distribution of sequences along event data records as well as group the results according to user-selected similarity preferences. We have identified a set of similarity metrics that are specific to event-sequences which we use as input into a clustering algorithm. The user can choose which metrics to use and assign weighting factors to them, which results in groupings that exhibit similar behaviour according to their definition of similarity and interestingness. The resulting clusters can be interactively explored in a multiple linked-view environment showing the clusters, the cluster quality, the similarity metrics and meta (background) information describing the clustered individuals in order to make comparisons within and between groups. Using such an interactive approach that considers user preferences and takes advantage of background knowledge gives a basis for enhanced analytical reasoning by providing a more complete understanding of the retrieved groupings and can lead to a more thorough analysis and accurate assessments.

    Nyckelord
    Event-based data, activity diary data, event sequences, similarity metrics, clustering, interactive exploration
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-58310 (URN)
    Tillgänglig från: 2010-08-10 Skapad: 2010-08-10 Senast uppdaterad: 2015-09-22
  • 16.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Andersson, Gunnel
    FoU Sodertorn, Sweden; Stockholm Univ, Sweden.
    Ellegård, Kajsa
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Stefansson, Claes-Göran
    Stockholm Univ, Sweden.
    Topor, Alain
    Stockholm Univ, Sweden; Univ Agder, Norway.
    Denhov, Anne
    Stockholm Univ, Sweden.
    Bulow, Per
    Jonkoping Univ, Sweden.
    A time-geographic approach for visualizing the paths of intervention for persons with severe mental illness2017Ingår i: Geografiska Annaler. Series B, Human Geography, ISSN 0435-3684, E-ISSN 1468-0467, Vol. 99, nr 4, s. 341-359Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Living conditions for persons with severe mental illness (SMI) in Sweden have changed dramatically in recent decades, mainly due to the closure of mental hospitals in the 1990s and the subsequent development of community-based interventions. Thereby, people with SMI have experienced care interventions in various forms, which vary according to how the treatment is institutionally organised over the years. There is, however, a lack of knowledge concerning what "care paths" persons with SMI have undergone in this fragmented institutional landscape. In this article we present a time-geography-inspired visualisation method to address this. A set of 437 persons, first diagnosed with psychosis between 2000-2004, were studied over 10 years with regard to their contact with various care institutions. We constructed time-geographic paths of intervention for these individuals and visualised them at an aggregate level. The initial exploration conducted using the proposed visualisation method showed gender and age differences in some respects, but also that the initial periods after the psychosis diagnoses were similar in terms of in-patient care interventions among men and women. The proposed visualisation method is promising and should be further developed for deeper analysis of long-term individual paths of intervention.

  • 17.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Andrienko, Gennady
    University of Bonn and Fraunhofer Institute IAIS, Germany.
    Andrienko, Natalia
    University of Bonn and Fraunhofer Institute IAIS, Germany.
    Interactive visual analysis of event-based movement data extracted from phone call records2012Ingår i: Geoinformationssysteme: Beiträge zum 17. Münchner Fortbildungsseminar 2012 / [ed] Koch, Kutzner, Eder, Munich, Germany: Wichmann , 2012Konferensbidrag (Övrigt vetenskapligt)
  • 18.
    Vrotsou, Katerina
    et al.
    Fraunhofer Institute IAIS, Sankt Augustin, Germany.
    Andrienko, Natalia
    Fraunhofer Institute IAIS, Sankt Augustin, Germany.
    Andrienko, Gennady
    Fraunhofer Institute IAIS, Sankt Augustin, Germany.
    Jankowski, Piotr
    San Diego State University, CA, USA.
    Exploring City Structure from Georeferenced Photos Using Graph Centrality Measures2011Ingår i: Machine Learning and Knowledge Discovery in Databases: European Conference, ECML PKDD 2011, Athens, Greece, September 5-9, 2011, Proceedings, Part III / [ed] Dimitrios Gunopulos, Thomas Hofmann, Donato Malerba, Michalis Vazirgiannis, Springer, 2011, s. 654-657Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    We explore the potential of applying graph theory measures of centrality to the network of movements extracted from sequences of georeferenced photo captures in order to identify interesting places and explore city structure. We adopt a systematic procedure composed of a series of stages involving the combination of computational methods and interactive visual analytics techniques. The approach is demonstrated using a collection of Flickr photos from the Seattle metropolitan area.

  • 19.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Bergqvist, Mathias
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Ellegård, Kajsa
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    PODD: A Portable Diary Data Collection System2014Ingår i: AVI '14 Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces, New York: Association for Computing Machinery (ACM), 2014, s. 381-382Konferensbidrag (Refereegranskat)
    Abstract [en]

    Activity diaries are a powerful data source for studying the time use of individuals and for creating awareness of individuals' daily activity patterns. The presented project is concerned with the development of an easily accessible method for collecting and analyzing diary data which will be applicable across a wide range of industrial, governmental, social science and medical domains. The PODD (POrtable Diary Data collection) is composed of a smartphone application for data registration, a web interface for user registration and an administration system for configuring the application according to the focus of the data collection.

  • 20.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew D.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Interactive Visual Exploration of Time-Use Data2006Ingår i: 10th IEEE International Conference on Information Visualisation, Los Alamitos, CA, USA: IEEE Computer Society , 2006, s. 93-94Konferensbidrag (Övrigt vetenskapligt)
  • 21.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Ellegård, Kajsa
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Everyday Life Discoveries: Mining and Visualizing Activity Patterns in Social Science Diary Data2007Ingår i: IEEE International Conference on Information Visualisation,2007: ISSN 1550-6037 / [ed] Ebad Banissi, Remo Aslak Burkhard, Georges Grinstein, Urska Cvek, Marjan Trutschl, Liz Stuart, Theodor G Wyeld, Gennady Andrienko, Jason Dykes, Mikael Jern, Dennis Groth and Anna Ursyn, Los Alamitos, CA, USA: IEEE , 2007, s. 130-138Konferensbidrag (Refereegranskat)
    Abstract [en]

    The ability to identify and examine patterns of activities is a key tool for social and behavioural science. In the past this has been done by statistical or purely visual methods but automated sequential pattern analysis through sophisticated data mining and visualization tools for pattern location and evaluation can open up new possibilities for interactive exploration of the data. This paper describes the addition of a sequential pattern identification method to the visual activity-analysis tool, VISUAL-TimePAcTS, and its effectiveness in the process of pattern analysis in social science diary data. The results have shown that the method correctly identifies patterns and conveys them effectively to the social scientist in a manner that allows them quick and easy understanding of the significance of the patterns.

  • 22.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Ellegård, Kajsa
    Linköpings universitet, Institutionen för tema, Tema teknik och social förändring. Linköpings universitet, Filosofiska fakulteten.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Exploring time diaries using semi-automated activity pattern extraction2009Ingår i: electronic International Journal of Time Use Research (eIJTUR), Vol. 6, nr 1, s. 1-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Identifying patterns of activities in time diaries in order to understand the variety of daily life in terms of combinationsof activities performed by individuals in different groups is of interest in time use research. So far, activitypatterns have mostly been identified by visually inspecting representations of activity data or by using sequencecomparison methods, such as sequence alignment, in order to cluster similar data and then extract representativepatterns from these clusters. Both these methods are sensitive to data size, pure visual methods becometoo cluttered and sequence comparison methods become too time consuming. Furthermore, the patterns identifiedby both methods represent mostly general trends of activity in a population, while detail and unexpectedfeatures hidden in the data are often never revealed. We have implemented an algorithm that searches the timediaries and automatically extracts all activity patterns meeting user-defined criteria of what constitutes a validpattern of interest for the user’s research question. Amongst the many criteria which can be applied are a timewindow containing the pattern, minimum and maximum occurrences of the pattern, and number of people thatperform it. The extracted activity patterns can then be interactively filtered, visualized and analyzed to revealinteresting insights. Exploration of the results of each pattern search may result in new hypotheses which can besubsequently explored by altering the search criteria. To demonstrate the value of the presented approach weconsider and discuss sequential activity patterns at a population level, from a single day perspective.

  • 23.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Ellegård, Kajsa
    Linköpings universitet, Filosofiska fakulteten. Linköpings universitet, Institutionen för tema, Tema teknik och social förändring.
    Cooper, Matthew D.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Exploring Time Diaries Using Semi-Automated Activity Pattern Extraction2007Ingår i: IATUR - XXIX Annual Conference,2007, 2007Konferensbidrag (Refereegranskat)
  • 24.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Forsell, Camilla
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    A Qualitative Study of Similarity Measures in Event-Based Data2011Ingår i: Human Interface and the Management of Information. Interacting with Information: Symposium on Human Interface 2011, Held as Part of HCI International 2011, Orlando, FL, USA, July 9-14, 2011, Proceedings, Part I / [ed] Michael J. Smith and Gavriel Salvendy, Berlin/Heidelberg: Springer, 2011, s. 170-179Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    This paper presents an interview-based study of the definition of sequence similarity in different application areas of event-based data. The applicability of nine identified measures across these areas is investigated and discussed. The work helps highlight what are the core characteristics sought when analysing event-based data and performs a first validation of this across disciplines. The results of the study make a solid basis for follow-up evaluations of the practical applicability and usability of the similarity measures.

  • 25.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Forsell, Camilla
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    2D and 3D Representations for Feature Recognition in Time Geographical Diary Data2010Ingår i: Information Visualization, ISSN 1473-8716, E-ISSN 1473-8724, Vol. 9, nr 4, s. 263-276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Time geographical representations are becoming a common approach to analysing spatio-temporal data. Such representations appear intuitive in the process of identifying patterns and features as paths of populations form tracks through the 3D space, which can be seen converging and diverging over time. In this article, we compare 2D and 3D representations within a time geographical visual analysis tool for activity diary data. We identify a representative task and evaluate task performance between the two representations. The results show that the 3D representation has benefits over the 2D representation for feature identification but also indicate that these benefits can be lost if the 3D representation is not carefully constructed to help the user to see them.

  • 26.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Fuchs, Georg
    Fraunhofer Institute IAIS, Sankt-Augustin, Germany.
    Andrienko, Natalia
    Fraunhofer Institute IAIS, Sankt-Augustin, Germany; City University London, London, UK.
    Andrienko, Gennady
    Fraunhofer Institute IAIS, Sankt-Augustin, Germany; City University London, London, UK.
    An Interactive Approach for Exploration of Flows Through Direction-Based Filtering2017Ingår i: Journal of Geovisualization and Spatial Analysis, ISSN 2509-8810, Vol. 1, nr 1-2, artikel-id 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is concerned with the representation and exploration of flows, defined as spatial interactions between geographic locations. Flows are challenging to display in a comprehensible manner due to the nature of the data, which are characterized by many crossings and overlaps leading to clutter. A number of different strategies have been suggested for addressing this problem, which commonly involve reducing the search space, aggregating the data or simplifying the representations often at the cost of information loss or distortion of spatial context. We propose an interactive approach for exploring large and highly connected networks of flows without distorting the geographical space and without losing the context overview in the process. The approach is based on a flow-specific interaction technique for filtering the data by direction, that enables an analyst to successively identify underlying spatial arrangement patterns. We illustrate our approach through exploring flows of tourists and locals in the Greater London area.

  • 27.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Janetzko, Halldor
    University of Konstanz, Germany.
    Navarra, Carlo
    Linköpings universitet, Institutionen för tema, Tema vatten i natur och samhälle. Linköpings universitet, Filosofiska fakulteten.
    Fuchs, Georg
    University of Bonn, Germany.
    Spretke, David
    University of Konstanz, Germany.
    Mansmann, Florian
    University of Konstanz, Germany.
    Andrienko, Natalia
    University of Bonn, Germany.
    Andrienko, Gennady
    University of Bonn, Germany.
    SimpliFly: A Methodology for Simplification and Thematic Enhancement of Trajectories2015Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 21, nr 1, s. 107-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Movement data sets collected using todays advanced tracking devices consist of complex trajectories in terms of length, shape, and number of recorded positions. Multiple additional attributes characterizing the movement and its environment are often also included making the level of complexity even higher. Simplification of trajectories can improve the visibility of relevant information by reducing less relevant details while maintaining important movement patterns. We propose a systematic stepwise methodology for simplifying and thematically enhancing trajectories in order to support their visual analysis. The methodology is applied iteratively and is composed of: (a) a simplification step applied to reduce the morphological complexity of the trajectories, (b) a thematic enhancement step which aims at accentuating patterns of movement, and (c) the representation and interactive exploration of the results in order to make interpretations of the findings and further refinement to the simplification and enhancement process. We illustrate our methodology through an analysis example of two different types of tracks, aircraft and pedestrian movement.

  • 28.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Johansson, Jimmy
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    ActiviTree: Interactive Visual Exploration of Sequences in Event-Based Data Using Graph Similarity2009Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, ISSN 1077-2626, Vol. 15, nr 6, s. 945-952Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The identification of significant sequences in large and complex event-based temporal data is a challenging problem with applications in many areas of todays information intensive society. Pure visual representations can be used for the analysis, but are constrained to small data sets. Algorithmic search mechanisms used for larger data sets become expensive as the data size increases and typically focus on frequency of occurrence to reduce the computational complexity, often overlooking important infrequent sequences and outliers. In this paper we introduce an interactive visual data mining approach based on an adaptation of techniques developed for web searching, combined with an intuitive visual interface, to facilitate user-centred exploration of the data and identification of sequences significant to that user. The search algorithm used in the exploration executes in negligible time, even for large data, and so no pre-processing of the selected data is required, making this a completely interactive experience for the user. Our particular application area is social science diary data but the technique is applicable across many other disciplines.

  • 29.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Nordman, Aida
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Exploratory visual sequence mining based on pattern-growth2019Ingår i: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 25, nr 8, s. 2597-2610Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sequential pattern mining finds applications in numerous diverging fields. Due to the problem's combinatorial nature, two main challenges arise. First, existing algorithms output large numbers of patterns many of which are uninteresting from a user's perspective. Second, as datasets grow, mining large number of patterns gets computationally expensive. There is, thus, a need for mining approaches that make it possible to focus the pattern search towards directions of interest. This work tackles this problem by combining interactive visualization with sequential pattern mining in order to create a "transparent box" execution model. We propose a novel approach to interactive visual sequence mining that allows the user to guide the execution of a pattern-growth algorithm at suitable points through a powerful visual interface. Our approach (1) introduces the possibility of using local constraints during the mining process, (2) allows stepwise visualization of patterns being mined, and (3) enables the user to steer the mining algorithm towards directions of interest. The use of local constraints significantly improves users' capability to progressively refine the search space without the need to restart computations. We exemplify our approach using two event sequence datasets; one composed of web page visits and another composed of individuals' activity sequences.

  • 30.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Vitoria, Aida
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Interactive Visual Sequence Mining Based on Pattern-Growth2014Ingår i: IEEE Conference on Visual Analytics Science and Technology (VAST), Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 285-286Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sequential pattern mining aims to discover valuable patterns from datasets and has a vast number of applications in various fields. Due to the combinatorial nature of the problem, the existing algorithms tend to output long lists of patterns that often suffer from a lack offocus from the user perspective. Our aim is to tackle this problemby combining interactive visualization techniques with sequential pattern mining to create a “transparent box” execution model for existing algorithms. This paper describes our first step in this direction and gives an overview of a system that allows the user to guide the execution of a pattern-growth algorithm at suitable points, through a powerful visual interface.

  • 31.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Ynnerman, Anders
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Are we what we do? Exploring group behaviour through user-defined event-sequence similarity2014Ingår i: Information Visualization, ISSN 1473-8716, E-ISSN 1473-8724, Vol. 13, nr 3, s. 232-247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The study of human activity in space and time is an inherent part of human geography. In order to perform such studies, data on the time use of individuals, in terms of sequence and timing of performed activities, are collected and analysed. A common assumption when analysing individuals’ time use is that groups that exhibit similar background and demographic characteristics also display similarities in how they use their time to structure their daily lives. In this article, we set out to investigate the correctness of such assumptions. We propose a visual analytics process based on sequence similarity measures tailored to event-based data such as performed activity sequences. The process allows an analyst to retrieve similarly behaving records according to user-selected similarity preferences and interactively explore aspects of this similarity in a multiple linked-view environment.

  • 32.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Ynnerman, Anders
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Behaviour-driven clustering based on event-sequence similarity metrics2010Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    When analysing event data two key objectives are to first identify interesting subsequences in the data records and then to retrieve groups of records that exhibit similar behaviour. This is especially true when the focus of the exploration is the human, for example when using activity diaries to reveal sub-populations with similar behaviour, medical records to identify groups with similar medical conditions, or web sessions to find groups with similar web-surfing habits. In this paper we propose a visual exploration approach, based on sequence similarity metrics and clustering techniques, that will allow an analyst to interactively explore the distribution of sequences along event data records as well as group the results according to user-selected similarity preferences. We have identified a set of similarity metrics that are specific to event-sequences which we use as input into a clustering algorithm. The user can choose which metrics to use and assign weighting factors to them, which results in groupings that exhibit similar behaviour according to their definition of similarity and interestingness. The resulting clusters can be interactively explored in a multiple linked-view environment showing the clusters, the cluster quality, the similarity metrics and meta (background) information describing the clustered individuals in order to make comparisons within and between groups. Using such an interactive approach that considers user preferences and takes advantage of background knowledge gives a basis for enhanced analytical reasoning by providing a more complete understanding of the retrieved groupings and can lead to a more thorough analysis and accurate assessments.

  • 33.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Ynnerman, Anders
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Cooper, Matthew D.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Visuell informationsteknologi och applikationer. Linköpings universitet, Tekniska högskolan.
    Seeing Beyond Statistics: Visual Exploration of Productivity on a Construction Site2008Ingår i: Vis 2008, Visualisation: Visualisation in Built and Rural Enviroments, Los Alamitos, CA, USA: IEEE Computer Society, 2008, s. 37-42Konferensbidrag (Refereegranskat)
    Abstract [en]

    Work on the construction site is known to be inefficient due to workers spending much time waiting for materials, transporting materials and from frequent interruptions of tasks. Studies on the construction site typically use statistical measures to analyse the sampled data about work and such measures, while very useful, can overlook important features of the data. In this paper we apply a previously developed approach, derived from Time Geographical methods, to visually represent the sampled construction productivity data and show that this method may enable the analyst to better understand the distribution of activities, and how they are interrelated and dependent upon each other. 

  • 34.
    Vrotsou, Katerina
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Zhi, Haolin
    Fraunhofer IAIS, Sankt Augustin, Germany.
    Peca, Iulian
    Fraunhofer IAIS, Sankt Augustin, Germany.
    Andrienko, Gennady
    Fraunhofer IAIS, Sankt Augustin, Germany.
    Andrienko, Natalia
    Fraunhofer IAIS, Sankt Augustin, Germany.
    Interactive Exploration of Events and Presence of People in Space and Time through KD-Photomap2012Ingår i: AVI '12 Proceedings of the International Working Conference on Advanced Visual Interfaces / [ed] Negulescu M.; Ruiz J.; Lank E.; Li Y., ACM Press, 2012, s. 804-805Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    We explore people's activities in space and time by analysing publicly available georefenced photographs. We do this using KD-photomap, a web-based visual analytics system for exploring collections of Flickr photographs and meta-data associated with them. The system provides an interface for flexible browsing of photographs in search of interesting pictures, and places, and also a framework for exploration of presence and identification of events in space and time.

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