# Re: st: Collapse with sum function and missing values

 From Michael Mitchell To statalist@hsphsun2.harvard.edu Subject Re: st: Collapse with sum function and missing values Date Wed, 10 Feb 2010 14:13:09 -0800

```Thanks all, both for the general thoughts on the underlying rationale
for this, as well as the practical suggestions. As some noted, I could
do this...

. collapse (sum) x (count) nonmiss=x, by(group)
. replace x=. if nonmiss==0

I have about 100 "x" values, and there is no pattern to the names. All
methods I can think of for ensuring that the "x" values are . when all
members of the group are . involve either substantial typing or a fair
amount of programming. Am I overlooking a simple solution for this?

Thanks,

Michael

On Wed, Feb 10, 2010 at 7:14 AM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
>
>
> As in http://www.stata.com/statalist/archive/2010-02/msg00428.html ?
>
>
>
> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Elizabeth
> Allred
> Gesendet: Mittwoch, 10. Februar 2010 16:12
> An: statalist@hsphsun2.harvard.edu
> Betreff: Re: st: Collapse with sum function and missing values
>
> 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
> <1F1A9AC9-4E03-488D-ADA4-971B6A192CEE@bc.edu>, Kit Baum <baum@bc.edu> 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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```