IAT 355 Visual Analytics Encoding Information: Design · Lines encourage trends IAT 355 | Design...

IAT 355 Visual Analytics

Encoding Information: Design Lyn Bartram

4 stages of visualization design

IAT 355 | Design Idioms 2

Recall: Data Abstraction

•  Tables •  Data item (row) with attributes (columns) : row=key, cells = values

•  Networks •  Item (node) with attributes (features) and relations (links) •  Trees (hierarchy) •  Node = key, node-node, link = key, cell = value

•  Text/Logs •  Grammar •  Bag of words •  Derived values

•  Image •  2d location = key, pixel value expresses single attribute or combo of attributes

according to coding (RGB)

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A Framework for Analysis (Munzner)

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Design IDIOM

Visualization: Why?

Analyze, Explore, Discover

Explain, Illustrate, Communicate

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Munzner

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Why does not define how completely

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Designing Vis Idioms (Munzner)

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Review: (Munzner)

•  Marks Points Lines Areas

•  Channels Position hue Size saturation Shape lightness orientation texture …

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What is this? How Much/many of something is there?

Credit: T. Munzner, 2014

Fundamental principles

Expressiveness: •  the visual encoding should express all of, and only, the

information in the dataset attributes

Effectiveness: •  the importance of the attribute should match the

salience of the channel. •  Use the strongest and most accurate channels for the

most important interpretation tasks (data)

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IAT 355 | Design Idioms 12

Credit: T. Munzner, 2014

Space

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Slide adapted from David Lippman's

Perfect positive Strong positive Positive correlation r = 1 correlation r = 0.99 correlation r = 0.80

Strong negative No Correlation Non-linear correlation r = -0.98 r = 0.16 relationship

However …

•  Scatter plots can be difficult to understand

•  What alternatives are there?

•  More generally, what kinds of techniques are best for what kinds of problems?

Scatterplot as idiom

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Circumference (ft)

Heig

ht (f

t)

Bar chart idiom

•  Categorical attributes match well with spatial regions

•  Separate, order, align

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Credit: T. Munzner, 2014

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Few’s correlation bar graph

Paired Bar graph with trend lines (Few)

Line Chart idiom

•  Line charts, dotplots •  Good for ordered data

IAT 355 | Design Idioms

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Mind the Gap - An Economic Chart Remake

What’s wrong?

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Lines encourage trends

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Je Zacks and Barbara Tversky. Bars and Lines: A Study of Graphic Communication." Memory and Cognition 27:6(1999), 1073{1079

Lines imply connections •  “the more male someone is the

taller he is”

Use when there is some ordered progression between the discrete categories on the x-axis •  “12 year olds are taller than 10

year olds”

Tufte’s Sparklines

•  Give a hint of the trend, but don’t show the actual axes and scales.

peer2patent.org

•  Good for dashboards and small spaces

Lines: Aspect ratio matters!

•  our ability to judge angles is more accurate at exact diagonals than at arbitrary direction •  We can judge distances “off” 45 or 90 degrees (43 ) but cannot see

the difference between 20 and 22 degrees •  Multiscale banking to 45 degrees – algorithm to compute informative

aspect ratios to maximise line segments close to the diagonal

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What about Pies?

Radial layouts

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radial idioms

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Idiom Star plot

What:data Table: 1 quant value, 1 categorical attribute

How: Encode length coding along point marks at 1D spatial position along axis + 1D spatial position for aligned axes

Idiom Pie chart

What:data Table: 1 quant value, 1 categorical attribute

How: Encode area and angle

Percent  Blue  rela,ve  to  Red?  

Percent  Blue  rela,ve  to  Red?  

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Few’s criteria for an effective visualization

•  Clearly indicate the nature of the relationship •  Represent the quantities accurately •  Makes it easy to compare the quantities •  Makes it easy to see the ranked order of values •  Makes obvious how people should use the information

Clearly indicate the nature of the relationship?

Represents quantities accurately?

Makes it easy to compare quantities?

Makes it easy to see ranked values?

Makes it easy to see how people should use information?

A better way

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body  

brain  

blood  

Percent  Water  

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body   brain   blood  

Percent  Water  

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body brain blood

Percent Water

Bad  

Be>er  

Even  Be>er*  

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Too Little

About Right

Too Much

National Spending to Deal with Drug Addiction

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Too Little

About Right

Too Much

National Spending to Deal with Drug Addiction

Male  

Female  

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Too Little

About Right

Too Much

National Spending to Deal with Drug Addiction

Female Male

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Male

Female

National Spending to Deal with Drug Addiction

Too Little

About Right

Too Much

h>p://chartchooser.juiceanaly,cs.com/  

Colour

Get it right in black & white

•  Value •  Perceived lightness/darkness •  Controlling value primary rule for design

•  Value defines shape •  No edge without lightness difference •  No shading without lightness variation

•  Value difference (contrast) •  Defines legibility •  Controls attention •  Creates layering

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Controls Legibility

IAT 355 | Design Idioms

colorusage.arc.nasa.gov

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Legibility

IAT 355 | Design Idioms

Drop Shadows

Drop Shadow Drop shadow adds edge Primary colors on black

Primary colors on black

Primary colors on black

Primary colors on black

Primary colors on black

Primary colors on black

Primary colors on white

Primary colors on white

Primary colors on white

Primary colors on white

Primary colors on white

Primary colors on white

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Readability

IAT 355 | Design Idioms

If you can’t use color wisely, it is best to avoid it entirely Above all, do no harm

If you can’t use color wisely, it is best to avoid it entirely Above all, do no harm.

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Why does the logo work?

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Why does this logo work so well?

IAT 355 | Design Idioms

Value control

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Contrast and Layering

•  Value contrast creates layering

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Context

Context

Normal

Normal

Urgent Context

Context

Normal

Normal

Urgent Context

Context

Normal

Normal

Urgent

colorusage.arc.nasa.gov

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What Defines Layering?

•  Perceptual features •  Contrast (especially lightness) •  Color, shape and texture

•  Task and attention •  Attention affects perception

•  Display characteristics •  Brightness, contrast, “gamma”

IAT 355 | Design Idioms

Emergency

Emergency

Emergency

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General guidelines … or from Tufte to practice [Stone, Ware]

•  Assign colour according to function •  Use contrast to highlight •  Use analogy to group

•  Control value contrast for legibility •  Break isoluminance with borders

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From principles to palettes

•  Limit palette to 2 or 3 colours and use variations within them

•  Different choices convey different messages

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Tableau Color Example

•  Color palettes •  How many? Algorithmic? •  Basic colors (regular and pastel) •  Extensible? Customizable?

•  Color appearance •  As a function of size •  As a function of background

•  Robust and reliable color names

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Tableau™ Colors

IAT 355 | Design Idioms

www.tableausoftware.com

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Maximum hue separation

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Analogous, yet distinct

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Sequential

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Stephen Few’s practical rules on colour

1.  If you want different objects of the same color in a table or graph to look the same, make sure that the background—the color that surrounds them—is consistent.

2.  If you want objects in a table or graph to be easily seen, use a background color that contrasts sufficiently with the object.

IAT 355 | Design Idioms

Don’t do this!

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Few (2)

3. Use colour only when needed to serve a particular communication goal

4. Use different colours only when they correspond to differences of meaning in the data

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Few (3)

5. Use soft, natural colors to display most information and bright and/or dark colors to highlight information that requires greater attention.

6. When using color to encode a sequential range of quantitative values, stick with a single hue (or a small set of closely related hues) and vary intensity from pale colors for low values to increasingly darker and brighter colors for high values.

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Few (4)

7. Non-data components of tables and graphs should be displayed just visibly enough to perform their role, but no more so, for excessive salience could cause them to distract attention from the data

8. Avoid using red/green display without redundant cueing 9. Avoid using visual effects in graphs

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