st: indicator variables from -by-

[László Sándor <sandorl@gmail.com>]

Hi,
I have so many observations that even the byte tempvars of
-marksample- might make me run out of memory.

But -by- must be inefficient in this, as if you -bys- over many groups
(e.g. households), you never run out of memory because a new touse
tempvar was created for each group.

Thus I don't understand why this wrapper for -sum, meanonly- (just to
collect saved results lost otherwise) runs out of copious amounts of
memory (bying over 20 groups) while the -bys: sum, meanonly- is still
much, much faster than any tabbing or tabstating or statsbying or Mata
alternative. What does -by- handle differently about the latter what
it cannot do with the former?

prog mymns, byable(recall, noheader)
 syntax [varlist] [if] [in]
 marksample touse
 sum `varlist' if `touse', mean
 mat A=nullmat(A)\r(mean)
end

Thanks,

Laszlo
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