SAS/IML Workshop: What they were thinking

The graphic is a scatterplot of the longitude and latitude of Napolean's army at a series of times. For each group of soldiers, the advance and retreat were plotted separately as paths. The cities were in a separate data set and were labeled with a single command. The bottom margin on the scatterplot was extended and that blank space used to draw the temperature time series.

The linear transformation of the Y-axis from the latitude scale to the temperature scale was explicitly programmed. While not difficult, using this technique to draw a second plot on the first is less intuitive than creating the first plot.

The next version of IML Workshop (version 2.1) has a built-in DrawPath command that simplifies the production of this graphic. Specifically, it does all the work of the module PlotContinuousDataPath and so that module is not needed.