Maybe I am wrong, but wouldn't it be easier, if you are interested in
those mean values, to do the following:
let x be an index of your observations
MEAN_ax = (ax * b1 - c1 + ax * b2 - c2 + ... ax * bN - cN) / N
MEAN_ax = [ax * (b1+b2+b3+...+bN) - c1+c2+c3+...cN)] / N
That reduces to, borrowing from Martin's code and adding some lines - the
following:
***************
sysuse auto, clear
*get the levels of mpg (a in your xmpl)
levelsof mpg, loc(levels)
*loop through them, create new vars along the way
*price takes place of b in your code, headroom is c
foreach lev of loc levels{
g result`lev'=`lev'*price- headroom
}
*get the means from -summarize-
su result*
/* new code */
egen f = total(price)
egen g = total(headroom)
egen fg = count(f)
gen testresult = (mpg*f-g)/fg
tab testresult
*************
- of course, that could be written more elegant...
Best regards,
Johannes
----------------------
Johannes Geyer
Deutsches Institut für Wirtschaftsforschung (DIW Berlin)
German Institute for Economic Research
Department of Public Economics
DIW Berlin
Mohrenstraße 58
10117 Berlin
Tel: +49-30-89789-258
[email protected] schrieb am 14/10/2008 13:49:38:
> I think it should be
>
> levelsof ICER_round, loc(levels)
> foreach lev of local levels {
> generate result`lev' = `lev' * Delta_Q - Delta_C
> }
>
> However, are you really sure you want to generate 10000 variables?
>
> Furthermore, should -levelsof- hits Stata's limits you could type
>
> mata: st_local("levels",
> mm_invtokens(strofreal(uniqrows(st_data(.,"ICER_round"))')))
>
> assuming that ICER_round is a numeric variable (-mormata- required,
> type -ssc describe moremata-).
>
> ben
>
> On Tue, Oct 14, 2008 at 1:24 PM, Martin Weiss <[email protected]>
wrote:
> > "levelsof may hit the limits imposed by your Stata. However, it is
> > typically used when the number of distinct values of varname is
modest."
> > (from -h levelsof-). I should have anticipated this problem. Are the
levels
> > of your "a" in any way regularly spaced (to enable application of
> > -forvalues-)?
> >
> >
> > HTH
> > Martin
> >
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]] On Behalf Of Carlo
Lazzaro
> > Sent: Tuesday, October 14, 2008 12:44 PM
> > To: [email protected]
> > Subject: st: how to work around -levelsof- limits with Stata 9.2/SE?
> >
> >
> > Dear Statalisters,
> > I have performed successfully Martin's helpful syntax using -levelsof-
on a
> > sample of 20 distinct values for var a.
> > However, when I tried to repeat the loop for the total 10,000 levels
of var
> > a I got an error message(admittedly, the recommended limit for
-levelsof- is
> > a modest number of distinct values for varlist, so I cannot complain
about
> > this useful ado.file). Is there any way to work this around?
> >
> > Please find below the command lines I typed along with the error
message I
> > got at the end of the sequence:
> >
> > . levelsof ICER_round, loc(levels) *around 10,000 levels are still
> > reported after rounding to the nearest whole number
> > . foreach lev of local levels {
> > 2. g result`lev'=` ICER_round'* Delta_Q- Delta_C
> > 3. }
> > invalid syntax
> > r(198);
> >
> > Thanks a lot for your kindness and for your time.
> >
> > Kind Regards,
> >
> > Carlo
> >
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