In reply to Paige Miller.

Correct, PROC FCMP does not support optional arguments and you need to supply all four argument values. While working on this piece I thought about it and gave it a try, but was not successful. Another option would be using the VARARGS option which allows you to pass all your arguments as a single array, but that's hardly a simplification. The FCMP procedure has many limitations, but for this implementation consider this as a small inconvenience price for universal functionality :)

My hope is that some day SAS will implement this function natively and include defaults and optional arguments as you suggest. Thank you for your input, Paige!