Visualizing Time (eBook)

Graham Wills is Visualization Architect and Principal Software Engineer for SPSS, Inc.

Visualizing Time 3
Preface 7
Acknowledgements 9
A Note on the Figures 11
Contents 13
1 History 17
1.1 The Importance of Time 17
1.2 Ancient Visualizations of Time 18
1.2.1 Summary 21
1.3 Playfair 22
1.3.1 Summary 24
1.4 Napoleon's March 25
1.4.1 A Fortunate Correlation 27
1.4.2 Summary 30
1.5 Comic Books 31
1.5.1 Summary 34
1.6 Further Exploration 36
2 Framework 37
2.1 How to Speak Visualization 37
2.2 Elements 39
2.2.1 Point 40
2.2.2 Line 41
2.2.3 Area 42
2.2.4 Interval 45
2.2.5 Schema 49
2.2.6 Multiple Elements 49
2.3 Statistics 51
2.3.1 Local Smooths 52
2.3.2 Complex Statistics 55
2.4 Aesthetics 57
2.4.1 Categorical and Continuous Aesthetics 60
2.4.2 Combining Aesthetics 62
2.5 Coordinates and Faceting 65
2.5.1 Coordinates 66
2.5.2 Faceting 71
2.6 Additional Features: Guides, Interactivity, Styles 72
2.6.1 Guides 72
2.6.2 Interactivity 74
2.6.3 Styles 74
2.7 Summary 77
2.8 Further Exploration 78
3 Designing Visualizations 79
3.1 Guiding Principles 79
3.1.1 The GQM Methodology 80
3.2 Goals 81
3.2.1 Presenting What Is Important 82
3.2.2 Seeing General Patterns 82
3.2.3 Spotting Unusual Features 84
3.3 Questions 85
3.3.1 One Variable: Unusual Values 86
3.3.2 One Variable: Showing Distribution 87
3.3.3 Two Variables: Showing Relationships and Unusual Values 89
3.3.3.1 Trends: One Variable Varying Over Time 93
3.3.4 Multiple Variables: Conditional Relationships, Groups, and Unusual Relationships 94
3.3.5 Multiple Variables: Showing Models 96
3.4 Mappings 101
3.5 Systems of Visualizations 102
3.5.1 Narrative Structure 104
3.5.2 Consistency 105
3.5.3 Stereotypes 105
3.6 Top-Down Versus Bottom-Up 105
3.7 Summary 107
3.8 Further Exploration 109
4 Types of Data 110
4.1 Four-Minute Mile, Day of the Week, Bottom of the Ninth 110
4.1.1 Scales of Measurement 111
4.1.2 Form Follows Function 112
4.2 Events and Intervals 114
4.3 Regular and Irregular Data 116
4.4 Date and Time Formats 117
4.5 Summary 118
4.6 Further Exploration 119
5 Time as a Coordinate 120
5.1 Put It on the Horizontal Axis 120
5.2 Event Occurrences 123
5.2.1 Many Events 129
5.3 Regular Categorical Sequences 131
5.3.1 Patterns in Sequences 133
5.4 Summary 136
5.5 Further Exploration 136
6 Coordinate Systems, Transformations, Faceting, and Axes 137
6.1 Time Series 137
6.1.1 Aspect Ratio 138
6.2 Coordinate Transformations 141
6.3 Axes 143
6.3.1 Drawing Time Axes 146
6.3.2 Formatting Time Ticks 149
6.4 Faceting 150
6.4.1 Faceting by Time 152
6.4.2 Faceting Complexity 154
6.4.3 Time Within a Faceting 158
6.4.4 Faceting When Data Are Not Categorical 162
6.5 Summary 164
6.6 Further Exploration 164
7 Aesthetics 165
7.1 Time as a Main Aesthetic 165
7.1.1 Representing Counts 166
7.1.2 Summarizing and Splitting Aesthetics 168
7.2 Specific Aesthetics 170
7.2.1 Coloring by Time 170
7.2.2 Sizing by Time 171
7.2.3 Shaping by Time 172
7.2.4 Other Aesthetics and Time 175
7.3 Time as a Secondary Aesthetic 175
7.4 Summary 179
7.5 Further Exploration 180
8 Transformations 182
8.1 Distortions of Time 182
8.2 Time as Frequency 185
8.3 Converting Between Categorical and Continuous 189
8.3.1 From Categories to Continuous 189
8.3.2 From Continuous to Categories 191
8.4 Summary 192
8.5 Further Exploration 193
9 Interactivity 194
9.1 A Framework for Interactivity 194
9.1.1 Display Pipeline 195
9.2 Modifying Parameters 197
9.2.1 Modifying Element Parameters 197
9.2.2 Modifying Aesthetic Parameters 199
9.2.3 Modifying Coordinate Parameters 201
9.2.4 Modifying Statistic Parameters 204
9.2.4.1 Fitting Seasonality Interactively 205
9.2.5 Modifying Scale Parameters 207
9.2.6 Modifying Facet Parameters 208
9.2.7 Modifying Transform Parameters 209
9.3 Interacting via the Data 209
9.3.1 Brushing and Linking 211
9.3.1.1 Selection Details 215
9.3.1.2 Nonboolean pseudovariable 217
9.3.2 Drill-down 217
9.3.3 Summary 218
9.4 Further Exploration 219
10 Topics In Time 220
10.1 Large Data Sets 220
10.1.1 Aggregration 221
10.1.2 Augmenting Traditional Displays 226
10.2 Time Lines and Linked Events 230
10.2.1 Linked Events 231
10.2.2 Timelines 233
10.3 Summary 237
10.4 Further Exploration 237
11 Gallery of Figures 239
11.1 Chart Complexity 239
11.1.1 Complexity Study Procedure 240
11.1.2 Initial Analysis 242
11.1.3 Model Fitting 245
11.1.4 Discussion 246
11.1.5 Application to the Figures in This Book 247
11.2 The Gallery 248
References 259
Index 265