I have to slightly disagree with Ian's point about purpose. Certainly, it can be very difficult to write a macro that returns the correct number of observations from a data set over a wide variety of situations. But, if you set out to do just that, you will not come up with short 10-20 line examples like we've seen here. You would need to construct an entire architecture that is fault-tolerant and fool-resistant. It takes time (see _nobs.sas in the Open Source SAS Macro Library as an example which took years). I suppose that's really his point. Not it can't be done, but it can't be done simply.

-- Rodney Sparapani Medical College of Wisconsin Sr. Biostatistician Patient Care & Outcomes Res. rsparapa@mcw.edu http://www.mcw.edu/pcor Was 'Name That Tune' rigged? WWLD -- What Would Lombardi Do