Steven Fraser
> > I am interested in obtaining the standard deviation for a
> particular
> > variable with groups determined by another variable.
> Essentially I would
> > like to combine the 'egen std()' function with the 'by'
> construct which is
> > not allowed. Is there an alternative to using collapse
> (I would prefer not
> > to change the dataset) or having to introducing a matrix?
Scott Merryman
> Or, if you want the standard deviation as a variable you could:
>
> levels class, local(levels)
> gen std = .
> foreach l of local levels {
> qui sum mpg if class == `l'
> qui replace std = r(sd) if class == `l'
> }
>
> You will need Nick Cox's -levels- (ssc install levels)
Scott's solution is fine (thanks for the plug),
but it also seems from Steven's wording that
-egen, sd()- will do what he wants (reference to -std()-
is a red herring here).
Nick
[email protected]
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