Re: st: RE: prtest and fweights

[Roger Newson <roger.newson@kcl.ac.uk>]

At 12:53 22/09/2004, Ronan M Conroy wrote:
> Nick Cox wrote:
>
> > I can't comment on why not. I guess no one asked, or no one thought of 
> > doing it.
> > For the moment,
> > preserve expand
> > prtest restore
> But beware  of -expand-. If an observation represents a zero frequency, it 
> will be retained. You will see a warning but it's a behaviour that you 
> might not have anticipated.
>
> I transcribe tables from papers that I am reviewing into Stata frequently, 
> to cross-check stats, and it's easy to transcribe a zero without 
> remembering that this will create a single observation in the expanded dataset.
A possible way around this problem is to use -expgen-, downloadable from 
SSC. -expgen- is an extended version of -expand-, and does not retain 
observations with a zero or missing value for the expression, unless the 
user specifies the -zero- or -missing- options. -expgen- can also generate 
new variables, containing the sequence number of the duplicate observation 
(amongst its duplicates in the new data set) and the position of its parent 
observation in the old data set.

Roger


--
Roger Newson
Lecturer in Medical Statistics
Department of Public Health Sciences
King's College London
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Opinions expressed are those of the author, not the institution.

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