The GCONTOUR Procedure

Overview

The GCONTOUR procedure produces plots that represent three-dimensional relationships in two dimensions. Lines or areas in a contour plot represent levels of magnitude (z) corresponding to a position (x, y) on a plane.

Use the GCONTOUR procedure to

examine trends in your data when they contain too many peaks and valleys to be accurately observed using the G3D procedure
examine data in which the levels, not the shape, of the data are important.
identify contour levels using lines or patterns.

Note: The GCONTOUR procedure produces rectangular contour plots, not irregular contour maps. [cautionend]

About Contour Plots

Contour plots represent the levels of magnitude of a variable z, called the contour variable, for a position on a plane given by the values of two variables x and y. Contour lines of different colors and line types show different levels of magnitude of z for locations of x and y.

Sample Contour Plot (GR14N01) shows a simple contour plot that illustrates the percentage of clay found in soil samples at various locations of a testing site. The x and y axes on the plot represent a graph of surface height at various x-y locations. The contour lines within the plot represent the locations on the plane that have the clay percentages specified in the legend. The program for this plot is in Generating a Simple Contour Plot.

By default, the GCONTOUR procedure automatically scales the axes to include the maximum and minimum data values, labels each axis with the name of its variable or an associated label, and draws a frame around the plot. In addition, it plots values using seven contour levels of the contour variable, representing those levels with default colors and line types. Finally, it generates a legend that is labeled with the contour variable's name.

Sample Contour Plot (GR14N01)

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