visualization of time-oriented...
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1 WOLFGANG AiGNER! visualization of time-oriented data
Wolfgang Aigner [email protected]
http://ifs.tuwien.ac.at/~aigner/
Version 4.0 June 3, 2013
visualization of time-oriented data
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About me
Basic and applied research + consulting projects
Focus: interactive visualization and data analysis of time-oriented data
60+ peer-reviewed publications
10+ years teaching experience
active member of scientific community InfoVis:Wiki – www.infovis-wiki.net TimeViz Browser – survey.timeviz.net EvalBench – www.evalbench.org
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Contents
Introduction What makes time a special data dimension?
What is time-oriented data?
Visualization Techniques Some selected techniques
Then: YOU decide, what we will look at
Roundup & Conclusions
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Data types 1-dimensional
2-dimensional
3-dimensional
Temporal
Multi-dimensional
Tree
Network
= 4D space “the world we are living in”
[Shneiderman, 1996]
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Spatial + temporal dimensions Every data element we measure is related and
often only meaningful in context of space + time
Example: price of a computer where? when?
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Differences between space and time Space can be traversered “arbitrarily”
we can move back to where we came from
Time is unidirectional we can’t go back or forward in time
Humans have senses for perceiving space visually, touch
Humans don’t have senses for perceiving time
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…travel in time virtually.
Interactive visualization Gives us the ability to…
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Time-oriented data?
Event calendar
Snow height & sunshine hours
Organization chart
iPod price
next >
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Event calendar
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Snow height & sunshine hours
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Organization chart
^ up
time
1998 2000 2002
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iPod price
^ up
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What is time?
“If no one asks me, I know. But if I wanted to explain it to one who asks me, I plainly do not know.” -- Augustinus (AD 354-430, The Confessions)
”Die Empfindung der Zeit hängt davon ab, auf welcher Seite
der geschlossenen Klotür man sich befindet.”
-- Albert Einstein
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What is time-oriented data?
no formal definition
what is considered as time-oriented data depends on the intended task
a possible definition:
Data, where changes over time or
temporal aspects play a central role or are of interest.
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Visualization of time-oriented data
What? time & data 1 Why? user tasks 2 How? visualization & interaction 3
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Modeling time
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Scale
ordinal only order is known
discrete every element of time has a unique predecessor and successor comparable to Integer
continuous between any two elements in time there might be another one
in between dense time comparable to Float
A B C
D
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Arrangement
linear
each element of time has a unique predecessor and a unique successor
cyclic
summer is before winter, but winter is also before summer
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Viewpoints
ordered
multiple perspectives
branching
Past Definite time - data
element assignment
Present Currently valid
state
Future Planning
Temporal uncertainty
Alternative scenarios
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Modeling time
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Granularity
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Calendar
System of granularities and mappings between them
representational scheme
for human readability and usability
Calendars Gregorian Academic (semester, trimester, ...) Financial (Quarters, Fiskal, ...) ...
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Example: Granularity paradoxon
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Time primitives
anchored
instant - single point in time
interval - duration between 2 instants
unanchored
span - duration of time
^ up
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Determinacy
determinate complete knowledge of temporal attributes
indeterminate incomplete knowledge of temporal attributes
no exact knowledge
i.e. “time when the earth was formed”
future planning
i.e. “it will take 2-3 weeks”
imprecise event times
i.e. “one or two days ago”
multiple granularities
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Characterizing data
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Relating data & time
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Visualization of time-oriented data
What? time & data 1 Why? user tasks 2 How? visualization & interaction 3
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Low-level Task List 1/2
Existence of a data element Does a data element exist at a specific time? Example: Was a measurement made in July, 1960? !
Temporal location When does a data element exist in time? Example: Is there a lecture taking place on November 24, 2005?
Time interval How long is the time span from beginning to end of the data element? Example: How long was the processing time for data set A?
Temporal texture How often does a data element occur? Example: How often was Jane sick last year?!
[McEachren, 1995]!
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Low-level Task List 2/2
Rate of change How fast is a data element changing or how much difference is there from
data element to data element over time?
Example: How much did the price of gasoline change since last September?
Sequence In what order do data elements appear?
Example: Did the explosion happen before or after the car accident?
Synchronization Do data elements exist together?
Example: Is Jill’s birthday on Easter Monday this year?
[McEachren, 1995]!
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Task Taxonomy 1/2 [Andrienko & Andrienko, 2006]!
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Task Taxonomy 2/2 [Andrienko & Andrienko, 2006]!
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Visualization of time-oriented data
What? time & data 1 Why? user tasks 2 How? visualization & interaction 3
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Visualization roots Statistics
Visualization of time-series.
The time-series plot is the most frequently used form of graphic design. [Tufte, 1983]
Mostly one parameter over time.
t!
y!
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Early time-series plot
Part of a text for monastery schools 10th or 11th century (!) Inclinations of the planetary orbits over time 800 years before other time-series plots appeared
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Train schedule
Paris to Lyon (1880s)
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Visualizing time-oriented data
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Visual mapping of time Dynamic: Time → Time (Animation)
probably the most natural form of mapping no “conversion” of concepts needed in between well suited for
keeping track of changes
following trends and movements
not well suited for
analytic and explorative tasks
no direct comparison of parameters between different points in
time is possible
Static: Time → Space
mapping of time to visual features direct comparison of parameters between different points in time is
possible
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Visual variables
position most common mapping
the most accurately perceived visual feature
length second most accurate attribute
typically, the length of an object denotes the duration, as for example in timelines!
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Visual variables angle, slope
analog-clock-based visualizations
!
connection connecting arrows or lines
“before element” --> “after element”
!
text, label simple text labelling
often combined with “connection”!
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Visual variables
line (thickness) Increasing or decreasing with time
color (brightness, saturation, hue) brightness most appropriate
“fading away” against the background
transparency
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Visual variables
area
enclosure
size
texture
shape
less suited
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Interaction facilitates active discourse with the data and visualization
see think
modify
[Card et al., 1983]
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Interacting with time
specific interaction techniques
+
task & interaction taxonomies
[VisuExplore project]
[VisuExplore project: measure tool]
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Interacting with time
specific interaction techniques
+
task & interaction taxonomies
[CHI09 workshop, VisuExplore project]
[Animated Scatterplot project]
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Interacting with time
specific interaction techniques
+
task & interaction taxonomies
[CHI09 workshop, VisuExplore project]
[CareCruiser project]
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Visualization of time-oriented data
What? time & data 1 Why? user tasks 2 How? visualization & interaction 3
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SELECTED VISUALIZATION TECHNIQUES
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Instant
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Sparklines
Simple, word-like graphics intended to be integrated into text
adds richer information about the development of a variable over time that words themselves could hardly convey
can be integrated seamlessly into paragraphs of text, can be laid out as tables, or can be used for dashboards
emphasis of first, last, min, and max value using colored dots
[Tufte, 2006]
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TimeSearcher
visualization tool for time-series data
timebox query model rectangular regions that specify constraints over time series data sets
x-axis extent: time period of interest
y-axis extent: constraint on the range of values
combinations of multiple timeboxes
data + query envelope
[Hochheiser, 2002; Hochheiser and Shneiderman, 2002]
DEMO http://www.cs.umd.edu/hcil/timesearcher/
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Horizon Graph
visualization technique for comparing a large number of time-dependent variables
based on the two-tone pseudo coloring
[Reijner, 2005]
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Cycle Plot
technique to make seasonal and trend components visually discernable
showing individual trends as line plots embedded within a plot that shows the seasonal pattern
mean value for each weekday as grey line
[Cleveland, 1994]
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Spiral Graph
encodes time-series data along a spiral
emphasizing the cyclic character of the time domain
data values are visualized using symbols for nominal data (left) as well as color and line thickness for quantitative data (right)
[Weber et al., 2001]
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ThemeRiver
Visualize thematic variations over time.
Across a large collection of documents.
River Metaphor: the “river” flows through time.
Changing width to depict changes.
Themes or topics are colored “currents”.
[Havre et al., 2000]
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Space-Time Cube
two spatial dimensions (latitude and longitude) along the x-axis and the y-axis
time along the z-axis
[Kraak, 2003]
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Interval
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Gantt Chart
Left: indented list of tasks
Right: timelines show position and duration of tasks
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PlanningLines
representation of temporal uncertainties
facilitates the identification of (un)defined attributes
supports in maintaining logical constraints (e.g., bars may not extend caps)
gives a visual impression of the individual and overall uncertainties
[Aigner et al., 2005]
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www.timeviz.net
Wolfgang Aigner • Silvia Miksch Heidrun Schumann • Christian Tominski
Visualization of Time-Oriented Data with a foreword by Ben Shneiderman
Springer
1st Edition., 2011, XVIII, 286 p. 221 illus., 198 in color. Hardcover, ISBN 978-0-85729-078-6.
Table of Contents Introduction • Historical Background • Time & Time-Oriented Data • Visualization Aspects • Interaction Support • Analytical Support • Survey of Visualization Techniques • Conclusion
NEW BOOK!
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3 Key Criteria
data frame of reference – abstract vs. spatial variables – univariate vs. multivariate
time arrangement – linear vs. cyclic time primitives – instant vs. interval
vis mapping – static vs. dynamic dimensionality – 2D vs. 3D
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survey.timeviz.net
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Visualization design
[Aigner, Miksch Schumann, Tominski, 2011]
What is presented? time and data
Why is it presented? user tasks
How is it presented? visual representation
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Roundup What makes time a special data dimension?
What is time-oriented data?
Concepts of time-oriented data
Visual variables for representing time
User Tasks for time-oriented data
Visualization techniques
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Conclusions time-oriented data covers a very broad field
what is considered as time-oriented data is task dependent
a lot of different techniques available
visualizations are task driven
periodic behavior is very common but relatively underexplored
Generally:
Visualization sparks interest for further investigation
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"Die Zeit verlängert sich für alle, die sie zu nutzen verstehen.” -- Leonardo Da Vinci
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