Laboratory Assignments

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Laboratory Assignments

• If time Visualization, Perception Cognition

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Readings

• Recall Handout 2
• New Reading Assignment

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Todays Schedule

• Presentations of Visual Analysis Projects
  (continued)
• Discussion of Static Design Assignment
• Discussion of Workshop Exercises
• If time Perception Cognition in Visualization
  Studies

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Visualizations of Home/House. Child Katrina
Survivors
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Recall House/Home (Katrina Victim)
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House/Home

• House as roof

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House?Home

• Sources Slide show of Katrina victims drawings
  of house/home, Dewann, S. Using Crayons to
  Exorcise Katrina, New York Times, Monday
  September 17, 2007, Arts Section, B1,5.

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Cognitive issues

• Visualization as a tool useful for
• aiding comprehension and understanding?

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Graphical visualization to support more efficient
task performance

• Allowing substitution of rapid perceptual
• influences for difficult logical inferences
• Reducing search for information required for task
  completion
• (Sometimes text is better, however)

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Issues

• Cognitive Artifacts
• Matching Representation to Task
• (Tic-tac-toe, flight schedules)
• Representations Aid Info Access and Computation
• (Medical prescriptions, Roman numerals,
  mapslegends)
• Naturalness and Experiential Cognition

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Cognitive Maps (1st Lab Exercise)

• You have some existing internal model of the
• system, stops, how to get there
• glance at SFU map for help
• Refine your internal model, clarifying items
• and extending it
• Note differences between your map the official
  one

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Process Models Navigation in Visual systems

• -process by which a person looks at a graphic and
  makes some use of it
• substeps
• Can you describe process?
• Navigation in visual systems - Creation and
  interpretation of an internal mental model

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Information foraging

• Search for schema (representation)
• Problem solve to trade off features
• Search for a new schema that reducesproblem to
  a simple trade-off
• Package the patterns found in someoutput product

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Navigation
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Crystallization
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Process
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Browsing

• Useful when
• Good underlying structure so that items close to
  oneanother can be inferred to be similar
• Users are unfamiliar with collection contents
• Users have limited understanding of how system
  isorganized and prefer less cognitively loaded
  methodof exploration
• Users have difficulty verbalizing
  underlyinginformation need
• Information is easier to recognize than describe

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User Tasks in Visualization Environments--Eleven
basic actions

• identify, locate, distinguish,
  categorize,cluster, distribution, rank, compare
  withinrelations, compare between
  relations,associate, correlate

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Data Types and Tasks
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Terminology

• Data case An entity in the data set
• Attribute A value measured for all datacases
• Aggregation function A function thatcreates a
  numeric representation for a setof data cases
  (eg, average, count, sum)

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Steps in Creating Visualization

• 1. Retrieve ValueGeneral DescriptionGiven a
  set of specific cases, find attributes ofthose
  cases.Examples- What is the mileage per gallon
  of the Audi TT?- How long is the movie Gone with
  the Wind?

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2. Filter

• General DescriptionGiven some concrete
  conditions on attribute values,find data cases
  satisfying those conditions.Examples- What
  Kelloggns cereals have high fiber?- What
  comedies have won awards?- Which funds
  underperformed the SP-500?

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3. Compute Derived Value

• General DescriptionGiven a set of data cases,
  compute an aggregatenumeric representation of
  those data cases.Examples- What is the gross
  income of all stores combined?- How many
  manufacturers of cars are there?- What is the
  average calorie content of Post cereals?

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4. Find Extremum

• General Description
• Find data cases possessing an extreme value of
  anattribute over its range within the data
  set.Examples- What is the car with the highest
  MPG?- What director/film has won the most
  awards?- What Robin Williams film has the most
  recentrelease date?

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5. Sort

• General DescriptionGiven a set of data cases,
  rank them according tosome ordinal
  metric.Examples- Order the cars by weight.-
  Rank the cereals by calories.

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6. Determine Range

• General DescriptionGiven a set of data cases
  and an attribute of interest,find the span of
  values within the set.Examples- What is the
  range of film lengths?- What is the range of car
  horsepowers?- What actresses are in the data set?

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7. Characterize Distribution

• General DescriptionGiven a set of data cases
  and a quantitative attribute ofinterest,
  characterize the distribution of that
  attributesvalues over the set.Examples- What
  is the distribution of carbohydrates in
  cereals?- What is the age distribution of
  shoppers?

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Find Anomalies

• General DescriptionIdentify any anomalies
  within a given set of data caseswith respect to
  a given relationship or expectation,e.g.
  statistical outliers.Examples- Are there any
  outliers in protein?- Are there exceptions to
  the relationship betweenhorsepower and
  acceleration?

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9. Cluster

• General DescriptionGiven a set of data cases,
  find clusters of similarattribute
  values.Examples- Are there groups of cereals
  w/ similar fat/calories/sugar?- Is there a
  cluster of typical film lengths?

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10. Correlate

• General DescriptionGiven a set of data cases
  and two attributes, determineuseful
  relationships between the values of those
  attributes.Examples- Is there a correlation
  between carbohydrates and fat?- Is there a
  correlation between country of origin and MPG?-
  Do different genders have a preferred payment
  method?- Is there a trend of increasing film
  length over the years?

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Compound tasks

• Sort the cereal manufacturers by average
  fatcontentCompute derived value Sort
• Which actors have co-starred with
  JuliaRoberts?Filter Retrieve value

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What questions were left out?

• Basic mathWhich cereal has more sugar, Cheerios
  or Special K?Compare the average MPG of
  American and Japanese cars.
• Uncertain criteriaDoes cereal (q, Y, Zj) sound
  tasty?What are the characteristics of the most
  valued customers?
• Higher-level tasksHow do mutual funds get
  rated?Are there car aspects that Toyota has
  concentrated on?
• More qualitative comparisonHow does the Toyota
  RAV4 compare to the Honda CRV?What other
  cereals are most similar to Trix?

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Concerns

• InfoVis tools may have influencedstudents
  questions
• Graduate students as group being studiedHow
  about professional analysts?
• Subjective Not an exact science

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Analytic gaps

• obstacles faced by visualizations in
  facilitating higher-level analytic tasks, such as
  decision making and learning.

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