Percent Stacked Area Plot

The percent stacked area plot is used to show the relative values of multiple variables over a range of dates or category values. The relative values of those variables sum to 100 percent over the range of values on the X axis. Because the stacked areas show proportions and not the total of the values for all variables, the plot includes a line showing how this total varies.

The dialog for displaying a percent stacked area plot

To produce this plot, the following must be specified:

  • Whether all of the data should be used, or only the data values highlighted on the map and in the table.

  • A variable for the X axis. This may be a date or categorical variable.

  • Two or more numeric variables to be shown on the Y axis, selected from the list on the left side of the dialog.

  • The method of aggregating values for a Y variable when there is more than one Y value for the same X value. Alternatives are the arithmetic mean (the default), the geometric mean, the harmonic mean, the median, and the sum.

The stacked area plot will be shown immediately after all necessary data are selected. Because there are default values for the other selections, the X and Y variables are all that may need to be selected.

Data rows with any missing data are not included in the plot.

The Y axis at the left side of the plot shows the percentages of the total represented by the Y variables. The Y axis at the right side of the plot shows the actual totals (sums) of the values.

The X axis label, left-hand Y axis label, and plot title can all be customized using the Alt-X, Alt-Y, and Alt-T keystrokes, respectively.

The “Source Data” button at the bottom of the dialog shows all of the selected data. The “Plot Data” button shows these data after summarization. These tables can be saved to a file with the Ctrl-S keystroke.