![A simple signum function](https://blogs.sas.com/content/iml/files/2011/08/t_signum.png)
The other day I needed to compute the signum function for each element of a matrix. If x is a real number, then the sgn(x) is -1 when x<0, 1 when x>0, and 0 when x=0. I wrote a SAS/IML module that contains a compact little expression: proc iml; start