Chapter 47: The G3GRID Procedure

Overview

The G3GRID procedure processes an existing SAS data set to create a data set that the G3D or GCONTOUR procedure can use to produce three-dimensional surface or contour plots. The procedure creates a data set whose horizontal (x and y) variable values form a complete grid, and it interpolates the value of the vertical (z) variables for each point on the x-y plane.

Using the G3GRID procedure, you can

• Create a rectangular grid of interpolated or smoothed values from irregularly spaced observations for use in a three-dimensional surface or contour plot.

• Complete a rectangular grid of interpolated or smoothed values for an input data set that has an insufficient number of observations to produce a three-dimensional surface or contour plot.

• Interpolate or smooth data for a three-dimensional graph.

The G3GRID procedure does not produce graphics output. Instead, it produces an output data set that you can use as the input data set for the G3D or GCONTOUR procedure.

Figure 47.1 on page 1328 and Figure 47.2 on page 1328 illustrate the effect of the G3GRID procedure on data.

Figure 47.1: Scatter Plot of Data Set Before G3GRID Processing

Figure 47.2: Surface Plot of Data Set After G3GRID Processing

Figure 47.1 on page 1328 shows a collection of data points, where z = f ( x , y ). These points are randomly distributed and cannot be displayed with a G3D surface plot, although they can be displayed with a scatter plot.

Figure 47.2 on page 1328 shows a surface plot of the data set that is created by a G3GRID interpolation of the original data set shown in Figure 47.1 on page 1328.

Note: The evenly distributed horizontal ( x , y ) data points form a grid for the three-dimensional graph.