When the chart contains a mapped point plot, one has the option of plotting the points in different symbols or colors based on a value associated with each point. This option can be accessed by choosing the point series in the bottom half of the window and clicking on the Symbols button under Additional Options. This will bring up the Point Styles window.
Additional options for mapped points. In order to signify values with different symbols chose the name of the point series in the list in the middle left (“locations” in the figure) then press the Symbols button under “Additional Options” to the right.
The Point Style window.
From the Point Style window you can choose whether points should be represented by a single symbol or multiple symbols. If Single is chosen from the Symbols box, all points will be listed as a single series and one should use the standard point formatting options to control the appearance of the points.
If Multiple is chosen from the Symbols box, then you must specify whether points should be distinguished by categories or values. Categories are unordered variables, usually represented by text labels or integers. Each category will get a unique symbol. Values are numeric and symbols will represent the relative magnitude of the associated value. Values can be sorted using the actual magnitude or by rank. One then needs to specify the matrix and column containing the values with which to distinguish the points. The matrix has to have the same number of rows as the number of coordinates being plotted. Finally, one can specify whether the different symbols should be distinguished by color, size, and/or shape.
(A)
(B)
Examples of mapping points with multiple symbols. (A) Color is used to represent categorical values (in this case, country); (B) Example of a bubble plot, where color and size are both used to distinguish rates of mortality due to oral cancer in males. Small, dark circles represent low mortality, large light circles represent high mortality.
After specifying how one wishes to distinguish points, each new symbol type will appear as a unique series in the top half of the editor window and can be edited individually as any other point series; the single collective data representing all of the points remains as an individual entry in the Additional Options section in the bottom-middle of the window.
The point pattern has been broken into multiple symbols, each listed as a unique series in the top half of the window, but still listed as a single group (“locations”) in the bottom half. The gradient bar is now an option and can be used to control the number of symbols and the default color scheme.
For plots with multiple symbols based on value, a color gradient is now an option for the point series as well; this gradient controls how many categories the points are broken into (the default is 10) as well as the default color scheme. Any changes made to the gradient will override changes made to individual series using the series editing options in the top half, so choose the number and color scheme you desire prior to editing individual series.