Data Visualization Methods for Transportation Agencies (2017) / Chapter Skim
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5 Choosing a chart type often means deciding among a set of familiar favorites. Popular choices include map, bar/column, line/area, donut/pie, flow, treemap, heat map, scatterplot, pictograph, and node-link diagrams.
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6 Tips: Tell the same story as your data Be aware of the disproportionate effect of sparsely populated areas when using choropleth maps. These colored maps are eye-catching and familiar, and generally well-understood, but can be misleading because tightly-packed, densely populated areas like inner cities may not even appear at the scale being displayed, while large rural areas will dominate the visual field, even though they may represent few people.
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7 Bar Charts Types of Data Bar charts require at least one quantitative dimension, which corresponds to the length of the bars, and one qualitative dimension, which is represented by different bars. Some variations can represent multiple quantitative and qualitative dimensions.
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8 Tools Basic Bars General Tools: Microsoft Excel, Google Sheets, Google Fusion Tables; Visualization Environments: Tableau, Qlik, Microsoft Power BI; and For Developers: D3.js, R, Google Chart API. Other Bar Types (Bullet, Histogram, Pyramid, Radial)
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9 If the chart is static, avoid showing points - A line without points looks sleek and uncluttered. Use line thickness to make a statement – Thicker lines make a bold statement and are easy to see.
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10 Improve memory and comprehension Avoid too many slices – Use no more than five to eight slices to ensure that readers can see differences among the slices. Avoid one very small slice –Small slivers are hard to distinguish and hard to label.
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11 Heat Maps Note: Choropleth maps and treemaps are sometimes called heat maps. Types of Data Quantitative values in an ordered field – Heat maps depend on assigning colors to a range of values, and the values must have a logical order such that adjacency is meaningful.
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12 Variations Scatterplot – Points are placed on a graph based on two values. An algorithm can be used to fit a line that passes through the points.
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13 Beware of volume distortion – if using icon size to show value, correlate to volume rather than height or width; use only one shape. Improve memory and comprehension Choose meaningful icons – Using emotional rather than abstract imagery (e.g., outlines of humans vs.
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14 Node-Link Diagrams Types of Data A finite set of nodes, each representing an entity – Nodes may have a quantitative value, which can be expressed by the size of the node. Nodes can have characteristics represented by color and size.
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15 2.3 · Common Techniques Additional techniques can be applied to make the visualization more interesting or more interactive, or to add additional dimensions of data, including: Combinations – Many of the different chart types can be combined to create hybrid chart types. For example, a bubble map can use pie charts instead of bubbles, combining the part-of-the-whole visualization of the pie with the location and magnitude visualization of the bubble map; Infographic – An infographic is a static display of data visualization charts and words to tell a story.
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