![Computing pairwise differences (efficiently, of course)](https://blogs.sas.com/content/iml/files/2011/08/t_pairwisediff.png)
The other day, someone asked me how to compute a matrix of pairwise differences for a vector of values. The person asking the question was using SQL to do the computation for 2,000 data points, and it was taking many hours to compute the pairwise differences. He asked if SAS/IML