In reply to Mxolisi Msiibi.

This question is unrelated to the blog post, so please ask questions like this at the SAS Support Communities. First read the article "Regression with restricted cubic splines in SAS." I suspect you can get the matrix by looking at the data set that is created by the OUTDESIGN= option. In SAS/IML, I think you can use the BSPLINE function to get the same information. See the first example in the BSPLINE documentation.