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From |
"Elizabeth Allred" <lizard@hsph.harvard.edu> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: Collapse with sum function and missing values |

Date |
Wed, 10 Feb 2010 10:12:22 -0500 |

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 > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**AW: st: Collapse with sum function and missing values***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**References**:**Re: st: Collapse with sum function and missing values***From:*Kit Baum <baum@bc.edu>

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