This section adds a legend that explains the different colors of lines in the graph. Adding a legend is usually accomplished by using the DrawLegend module that is distributed with SAS/IML Studio. The module is documented in the SAS/IML Studio online Help. The statements that follow show one choice for displaying a legend. Add these at the bottom of the program window, and select Program →Run from the main menu. Figure 8.2 shows how the legend appears.

   Labels = {"Least-Squares Fit" "95% Prediction Limits"};
   LabelSize = 8;            /* 8 point font */
   LineColor = BLUE || GRAY; /* form 1x2 matrix */
   LineStyle = SOLID;        /* all lines are solid */
   Symbol = -1;              /* no symbols */
   BackgroundColor = WHITE;
   Location = 'ILB';         /* Inside, Left, Bottom */
   run DrawLegend( FitPlot, Labels, LabelSize,
                     LineColor, LineStyle, Symbol,
                     BackgroundColor, Location );

Note the use of the SAS/IML concatenation operator ||. This operator takes the two predefined integers BLUE and GRAY and concatenates them into a matrix.

Note: Trying to form the matrix by using the following statement does not work because the SAS/IML language interprets that statement as forming a character matrix with values “BLUE” and “GRAY”:

   LineColor = {BLUE GRAY}; /* wrong! */

Similarly, as the next statement illustrates, you must use the concatenation operator when creating a matrix from submatrices. You cannot write

   Values = {N[2] NValue2[1]}; /* wrong! */