I've often wondered about the logic that the SGPLOT procedure in SAS uses to determine whether a set of graphical overlays will receive identical attributes or different attributes. (Recall that color, size, line style, and marker symbol are all examples of attributes.) I know that when you plot grouped data ("long-form" data by using the GROUP= option), each component of the plot gets a unique attributes by default. The situation is less clear when you are plotting wide data (multiple variab...
