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RE: st: RE: tab
-,subpop()- is like an -if-, or an additional -if- if there already is one;
it limits the set of observations that are tabulated. But the set of
values appearing in the table are not limited by the subpop variable, and
so, some cells can have zeroes. (When applied to two-way tabulations,
whole rows or columns might have all zeroes.)
I don't think you can successfully combine -,subpop()- with -bysort-,
because the limiting subpopulation would need to be different for each
value of the by-variable.
But you can do a separate -tab ..., subpop()- for each value of the
categorical variable that you would normally think of as your bysort
variable. If this is done to one-way tabulations, then each instance is
just like a column (or row) of a two-way tabulation, complete with cells
Thus, with the auto data, if all you want is the table for where foreign
==1, you can do...
tab rep78, subpop(foreign)
(This takes a shortcut, using the fact that foreign is coded 0 and 1. More
generally, you would do something such as...
gen byte foreign1 = foreign==1 // or "Foreign":origin
tab rep78, subpop(foreign1)
... and similarly for any other value corresponding to a desired limiting
But in this case, if you were to do...
gen byte foreign0 = foreign==0 // or "Domestic":origin
tab rep78, subpop(foreign0)
you would get the same result as...
tab rep78 if foreign==0
because there are no rep78 values beyond those seen within the set where
My comment about extending the dataset applies only if there are values of
the tabulated variable that exist nowhere in the dataset.
I hope this is useful (and correct).
At 04:01 PM 12/11/2003 +0000, you wrote:
Thanks for the reference to -, subpop()- which
somehow has never registered with me; indeed
I don't think I ever understood it.
Here is the sort of example I had in mind. Some
people would like explicit zeros in the case
of rep78 == 1, 2 & foreign == 1. Can -, subpop()-
help here, directly, without changing the dataset?
(This was one motivation for writing -tabcount-,
now on SSC. I thought that such tables should be
possible on the fly, so far as the user is
. bysort foreign : tab rep78
Institute for Policy Studies
Johns Hopkins University
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