>that's true, but SQL Server and MC Access both support it.
>Also, it is in the SQL standards. It doesn't matter how the Foxpro engine calculates it.

That I can't say - every application has its own little variations on SQL...the ones you mentioned make two passes through the data to do the work, so it will take extra time...vfp has it's own CALC way to do it, which may at least as fast or faster...

>
>Also, I wrote a UDF to calculate STDDEV in a single pass -
>(why I don't use it - it doesn't work with GROUP BY)
>here's how:
>It depends on PUBLIC variables to remember all average, count, sum and all the reqd. variables used to calculate STD. DEV.

PUBLICS shouldn't be used any more...and that's not a really single-pass. Your first pass, you get the sum. The second pass you use it to calculate the individual values (each X - SUM(X)/N)**2), etc.

But anyway, why not just use the "wheel" vfp provides, instead of trying to re-invent one? I write plenty of statistical functions in vfp for my work here, but not when they're already built in...