Overview

A contour plot displays relationships between three numeric variables in two dimensions. The plot displays level sets (contours) of a Z variable as a function of X and Y variables.

To create a contour plot using the GUI

1. Open or create a data table.

   For details, see Creating a Data Table.

2. Make sure the data table window is the active window.
3. On the Graph menu, click Contour Plot.

   IML Studio displays the Contour Plot dialog box.

4. Select a numeric variable that you believe to be a response function of two other variables (X and Y) and click Set Z.
5. Select a numeric predictor variable and click Set Y.
6. Select another numeric predictor variable and click Set X.
7. Click OK.

Contour plots display the most information when X and Y are nearly uncorrelated. The contour plot fits a piecewise-linear surface to the data, assuming that Z is a response function of X and Y. The contours are level-curves of the response function. By default, the range of the Z variable is divided into ten subintervals, and the ends of these subintervals are used as the heights at which to compute the level sets.

For a discussion of the BY Variables and BY Options tabs, see BY Group Processing: Using BY Group Processing.