Are you working in SAS/AF or SAS/FSP or a different development environment?   In SAS/AF the initial block of the object would allow you to filter data on either an environment variable value or  fixed code but the statement involved would most likely be either a KEEP (to keep variables) or DROP to remove variables. Basically similar but the syntax to list the explicit variables is usually shorter using one option over the other; want 5 of 50 variables then use Keep to list the 5, want 45 of 50 variables use Drop to remove the ones you don't.   RETAIN  is used to make the value of a variable propagate across records in a data step. ... View more