Statistical Graphics

Series Plots

You can use the SERIES subroutine to create a series plot, which is also known as a line plot. The subroutine requires two vector arguments: values for the X variable and values for the Y variable.

The following statements provide a simple example of creating a series plot. The PDF function evaluates the normal density function at evenly spaced points in the interval $[-5, 5]$. The SERIES subroutine creates the graph that is shown in Figure 16.10. 

proc iml;
x = do(-5, 5, 0.1);
y1 = pdf("Normal", x, 0, 1);

title "Series Plot with Default Properties";
run Series(x, y1);

Figure 16.10: Series Plot

Series Plot


For a more complicated example, the following statements create a series plot by using the GROUP=, OTHER=, GRID=, LABEL=, XVALUES=, and YVALUES= options. The result is shown in Figure 16.11. 

title "Series Plot with Groups and Reference Lines";
y2 = pdf("Normal", x, 0, 1.5);
g = repeat({1,2}, 1, ncol(x));   /* 1,1,1,...,2,2,2 */
x = x  || x ;
y = y1 || y2;

call Series(x, y) group=g                 /* assign color/marker shape */
                 other="refline -2 2 / axis=x"   /* add reference line */
                 grid={X Y}
                 label={"X" "Normal Density"}
                 xvalues=-4:4
                 yvalues=do(0,0.4,0.05);

Figure 16.11: Two Curves in a Series Plot

Two Curves in a Series Plot


The following list explains the options that are used to create Figure 16.11:

  • The GROUP= option specifies a vector of values that determine groups in the plot. In Figure 16.11, the two curves have different values of the grouping variable, which is set by using the g matrix.

  • The OTHER= option specifies statements in the SGPLOT procedure. In Figure 16.11, the REFLINE statement draws two horizontal lines on the plot.

  • The GRID= option specifies whether grid lines are displayed for the X and Y axes. Figure 16.11 shows grid lines for the Y axis.

  • The LABEL= option specifies axis labels for the X and Y axes. In Figure 16.11, both axes are labeled.

  • The XVALUES= option specifies a vector of values for ticks for the X axis. In Figure 16.11, the tick marks on the horizontal axis are spaced one unit apart in the interval $[-4, 4]$.

  • The YVALUES= option specifies a vector of values for ticks for the Y axis. In Figure 16.11, the tick marks on the vertical axis are spaced 0.05 units apart in the interval $[0, 0.4]$.