In reply to Hans.

Instructions for installing packages are part of the SAS/IML documentation. You install the package by using the PACKAGE INSTALL statement in a PROC IML program. The zip file will be unzipped automatically into the directories under the 'polygon' folder.

The polygon package was used only to illustrate convex hulls. It is not needed for the statistical portion of the article, which is visualizing a truncated predicted surface. You can safely delete the three statements that use the polygon package.