Essential Graphing • Treemaps • Example of Treemaps • Example using the Treemap Platform
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Example using the Treemap Platform
Treemaps can be useful in cases where histograms or bar charts are ineffective. This example uses the Cities.jmp sample data table, which contains meteorological and demographic statistics for 52 cities. Compare the bar chart to the treemap.
Create a bar chart representing ozone levels in each of the 52 cities:
1.
Select Help > Sample Data Library and open Cities.jmp.
2.
Select Graph > Legacy > Chart.
The launch window appears.
3.
Select OZONE and click Statistics.
4.
Select Mean.
5.
Select city and click Categories, X, Levels.
6.
Click OK.
The report window appears.
Figure 10.2 Ozone Levels in a Bar Chart
Although it is easy to see that there is a single large measurement, each bar looks similar. Subtle distinctions are difficult to see.
Create a treemap representing ozone levels in each of the 52 cities:
1.
Return to the Cities.jmp sample data table.
2.
Select Graph > Legacy > Treemap.
The launch window appears.
3.
Select POP (population) and click Sizes.
4.
Select city and click Categories.
5.
Select OZONE and click Coloring.
6.
Click OK.
The report window appears.
Figure 10.3 Ozone Levels in a Treemap
Compare the bar chart to the treemap. Because the treemap folds the data over two dimensions (size and color), each city’s data looks more distinctive than it did in the bar chart.
Note the following about this treemap:
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The magnitude of the ozone level for each city is represented by color (using JMP default colors).
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Each rectangle is colored based on a continuous color spectrum, with bright blue on the lowest end and bright red on the highest end. In this treemap, Des Moines has the lowest ozone levels, and Los Angeles has the highest ozone levels.
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Ozone levels somewhere in the middle decrease the intensity of the color, so pale blue, and pink indicate levels that are closer to the mean ozone level.
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Cities colored black have missing ozone values.
Tip: A photo can be displayed in the label when you place your cursor over a square. For example, in the Cities.jmp sample data table, you could add an Expression column that contains a photo of each city and add a label to the column. See Expression Role in the Using JMP book for details.

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Help created on 10/11/2018