The G3D procedure requires three numeric variables to produce a plot. The input data set forms a rectangular grid from the values of X and Y. One value of Z is required for each X-Y grid location. If multiple observations have the same Z value for any X-Y combination, only the last observation is plotted.

The G3D procedure requires nonmissing Z values for at least 50% of the grid cells. When the procedure cannot produce a satisfactory surface plot because of missing Z values, a warning message is issued and a graph might not be produced. To correct this problem, you can grid the data set with the G3GRID procedure. The G3GRID procedure interpolates the necessary values to produce a data set with nonmissing Z values for every X-Y combination. The G3GRID procedure can also smooth data for use with the G3D procedure. The output data set produced by the G3GRID procedure can be used as the input data set for the G3D procedure. See G3GRID Procedure for more information.

In order to properly scale the axes, the G3D procedure requires at least two observations. These observations must contain unique values for each of the three variables that are specified in the plot request. If these requirements are not met, an error message is issued, and a graph is not produced.

For both surface plots and scatter plots, the range of the Z axis is defined by the minimum and maximum data values for Z. To increase or decrease the range of the Z axis, you can use the ZMIN= option and the ZMAX= option in the PLOT or SCATTER statements. To restrict the range of an X axis or a Y axis, you can use a WHERE clause in the PROC step to subset the data. A DATA Step with a WHERE clause, or an IF statement can also be used to subset the data.