Re: st: St: collapse by _N

["Michael N. Mitchell" <Michael.Norman.Mitchell@gmail.com>]

Dear Ric

  In addition to the great answers Chris and Ulrich sent, I might suggest that you 
include a variable that counts the number of valid observations. After having the 
collapsed file, you could then decide what you might want to use as a threshold for the 
data being too unreliable. You can see more examples about collapsing, including examples 
using count, at http://www.ats.ucla.edu/stat/stata/modules/collapse.htm .

I hope this helps,

Michael N. Mitchell
Data Management Using Stata      - http://www.stata.com/bookstore/dmus.html
A Visual Guide to Stata Graphics - http://www.stata.com/bookstore/vgsg.html
Stata tidbit of the week         - http://www.MichaelNormanMitchell.com



On 2010-10-19 11.35 PM, Eric Uslaner wrote:
> Greetings,
>
> I have a survey data set with respondents geocoded.  I want to collapse the data set to the geocode level, so the simple command would be:
>
> collapse varlist,by(geocode)
>
> However some geocodes barely have any respondents and any collapsed data would be unreliable.  Is there a straightforward way to collapse only if the number of respondents is>  20 (e.g.)?
>
> Many thanks,
>
> Ric
>
>
>
>
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