Michael might use collapse (count) and then set his sum to missing when count=0.
>>> On 2/10/2010 at 10:06 AM, in message
<[email protected]>, Kit Baum <[email protected]> wrote:
<> >
> This is somewhat semantic. The presence of 3 and 4 in the group id suggests
> that such groups exist; they merely have no members in the present sample. It
> should be easy enough to -mvdecode- x==0 to x==.
>
> This reminds me of a grouse I had about the calculation of the s.d. of data
> that were all missing. The mean of these data was computed properly as
> missing, but the s.d. was reported as 0. Pedantically, as all values took on
> the same NAN value, there was indeed zero variance. I convinced StataCorp
> that this was not a good idea, and that the s.d. or variance of data that are
> all missing is indeed missing. That is now what -tabstat- does.
>
> Kit
>
> On Feb 10, 2010, at 2:33 AM, Michael wrote:
>
>> Shouldn't the value of -x- for groups 3 and 4 be missing, not zero.
>> To me, the sum of a series of missing values is a missing value. I am
>> doing a collapse for about 100 variables (100 x values) and need the
>> value to be defined as missing (not 0) in such cases. Any ideas?
>
>
> Kit Baum | Boston College Economics & DIW Berlin |
> http://ideas.repec.org/e/pba1.html
> An Introduction to Stata Programming |
> http://www.stata-press.com/books/isp.html
> An Introduction to Modern Econometrics Using Stata |
> http://www.stata-press.com/books/imeus.html
>
>
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