[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: Collapse with sum function and missing values

From   Kit Baum <>
Subject   Re: st: Collapse with sum function and missing values
Date   Wed, 10 Feb 2010 10:06:30 -0500

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.

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   |
                              An Introduction to Stata Programming  |
   An Introduction to Modern Econometrics Using Stata  |

*   For searches and help try:

© Copyright 1996–2020 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index