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(STATISTICAL) GRAPHS & CHARTS

Prof. Rahul C. Basole

CS/MGT 8803-DV > January 24, 2018

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HW1: DataVis Examples

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HW1: DataVis Examples

• Uber and Lyft in SF

– http://tncstoday.sfcta.org/

• Triple Play

– https://public.tableau.com/views/TriplePlayArt/Art?:embed=y&:display_count=no

&:showVizHome=no

• Medal Count

– http://www.nytimes.com/interactive/2008/08/04/sports/olympics/20080804_MED

ALCOUNT_MAP.html

• Corporate Pipeline by Gender

– https://www.scoopnest.com/user/ValaAfshar/650670269342875648

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Tumblr

• 48 students* = 48 vis-of-the-day submissions

• We will use a random order

• We will start next week

• Schedule will be on Canvas

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Project Pitch

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Today’s Agenda

• Learn about different statistical data graphs/charts

• Develop skill at choosing graph(s) to display different types of data

and data sets

• Learn approaches to address overplotting

• Understand concept of “banking to 45 degree”

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Scenario

you@company.com

sue_the_manager@company.com

URGENT: Need summary of performance reviews

I’ve interviewed three people for the new Customer Service Manager position and need to

summarize their qualifications for Jeff [the big boss]. He wants to choose the best candidate as

objectively as possible. After the colossal failure of my last hire, he no longer trusts my instincts.

I’ve attached a spreadsheet that rates each of the candidates according to the six areas of

competence that we use for performance reviews (experience, communication, etc.). Please

create a report that I can pass on to Jeff that presents my findings.

I’ll need it on my desk first thing tomorrow

Thanks,

Sue

performancereviews.xls

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Scenario

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Scenario

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Communicating Quantitative Data: A Design Process

There are six fundamental steps you should consider

1. Determine your message and identify your data

2. Determine if a table, or graph, or both is needed to communicate your message

The remaining steps apply only if one or more graphs are required

3. Determine the best means to encode the values

4. Determine where to display each variable

5. Determine the best design for the remaining objects

– Determine the range of the quantitative scale

– If a legend is required, determine where to place it

– Determine if tick marks are required and how many

– Determine the best location for the quantitative scale

– Determine if grid lines are required

– Determine what descriptive text is needed

6. Determine if particular data should be featured above the rest, and if so, how

Stephen Few “Effectively Communicating Numbers”

http://www.perceptualedge.com/articles/Whitepapers/Communicating_Numbers.pdf

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Some General Concepts

Table vs. Graph

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Some General Concepts

Recall: There are Different Data Types

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Some General Concepts

Common Relationships in Quantitative Data

CorrelationDistributionDeviation

Part-to-WholeRankingTime-Series

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Four types of objects work best for encoding quantitative values in graphs:

Points, Lines, Bars, Boxes

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Four types of objects work best for encoding quantitative values in graphs:

Points, Lines, Bars, Boxes

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Scatterplot for Correlation Analysis

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Scatterplot Matrix (“Crosstab”)

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Four types of objects work best for encoding quantitative values in graphs:

Points, Lines, Bars, Boxes

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Line Graphs

When to use:

When quantitative values change during a continuous period of time

more on this in our Temporal & Sequential Data lecture

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Line Graphs

Add Reference Lines

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Crosstab

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Which is increasing at a faster rate,

hardware sales or software sales?

Both at same rate, 10%

Log scale shows this

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Same chart, just drawn at

different aspect ratios.

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People interpret the diagrams

better when lines are around

45°, not too flat, not too steep

“Banking to 45°”

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Patterns

Daily sales Average per day

p. 176

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Four types of objects work best for encoding quantitative values in graphs:

Points, Lines, Bars, Boxes

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When to use:

When you want to support the comparison of individual values

Bar Charts

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Bar Charts

Vertical vs. Horizontal Bars

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Bar Charts

Reference Lines

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Four types of objects work best for encoding quantitative values in graphs:

Points, Lines, Bars, Boxes

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Boxplots

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Many other charts

Goal: Maximize Task-Data-Visualization Fit

Time-Series Analysis

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Many other charts

Goal: Maximize Task-Data-Visualization Fit

Distribution Analysis

Strip Plot

HistogramFrequency Plot

Stem-and-Leaf Plot

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Communicating Quantitative Data: A Design Process

Determine the best means to encode the values

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Communicating Quantitative Data: A Design Process

Determine where to display each variable

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Communicating Quantitative Data: A Design Process

Determine the best design for the remaining objects

Determine the Range for the Quantitative Scale

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Communicating Quantitative Data: A Design Process

Determine the best design for the remaining objects

If a Legend Is Required, Determine Where to Place It

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Communicating Quantitative Data: A Design Process

Determine the best design for the remaining objects

Determine If Grid Lines Are Required

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Too many data points.

Chart suffers from

data occlusion.

What are possible

techniques to

overcome ?

Communicating Quantitative Data: A Design Process

Determine the best design for the remaining objects

Overplotting

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Overplotting Solutions

• Reducing the number of values

– Aggregating the data

– Filtering the data

– Breaking the data into a series of separate graphs

– Statistically sampling the data

• Reducing size of data objects

• Removing all fill color from data objects

• Changing the shape of data objects

• Jittering data objects*

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Communicating Quantitative Data: A Design Process

Determine if particular data should be featured above the rest, and if so, how

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Real-World Dashboards

Multiple Concurrent Views

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Ok, let me get some feedback …

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What’s your Graph Design IQ?

• Let’s take a test.

• http://www.perceptualedge.com/files/GraphDesignIQ.html

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Reminder: Tableau Lab Tutorial

• Download and install Tableau

– Use the activation code posted on Canvas

• Download sample data file*

• Bring your laptop to class (hands-on tutorial)