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Re: st: RE: AW: irecode problem


From   Eva Poen <eva.poen@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: AW: irecode problem
Date   Thu, 5 Mar 2009 11:07:12 +0000

Kieran,

the title of the article says it all: lose the "evaluating equal sign"
in your code, and you should be fine. Especially in the lines

 local comm = "`comm'" + ", `p`i''"

and

 local comm = "`comm'" + ")"

The equal and plus signs are unnecessary.

Eva



2009/3/5 Kieran McCaul <kamccaul@meddent.uwa.edu.au>
>
> Thanks Martin, but that doesn't help.  Nick is merely pointing out that the 244 character limit can bite.
>
> ______________________________________________
> Kieran McCaul MPH PhD
> WA Centre for Health & Ageing (M573)
> University of Western Australia
> Level 6, Ainslie House
> 48 Murray St
> Perth 6000
> Phone: (08) 9224-2140
> Fax: (08) 9224 8009
> email: kamccaul@meddent.uwa.edu.au
> http://myprofile.cos.com/mccaul
> http://www.researcherid.com/rid/B-8751-2008
> ______________________________________________
> The fact that no one understands you doesn't make you an artist.
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Martin Weiss
> Sent: Thursday, 5 March 2009 5:45 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: AW: irecode problem
>
>
> <>
>
> With regard to the length issue, have you had a look at
> http://www.stata-journal.com/article.html?article=pr0045 yet?
>
>
>
>
> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Kieran McCaul
> Gesendet: Donnerstag, 5. März 2009 00:31
> An: statalist@hsphsun2.harvard.edu
> Betreff: st: irecode problem
>
> My problem is concerned with using the -irecode- function in a program
> when the number of cutpoints (the xi used in the function) varies.
>
> I'm accumulating probabilities across a number of groups and then
> picking someone from these groups at random based on these
> probabilities.  So I've approached this using the -irecode- function.  I
> sum the probabilities in each group and then create a running cumulative
> probability which I then append to the -irecode- function that I've
> store in a local as a string.  When someone is picked, I recalculate the
> cumulative probabilities excluding those who have already been picked.
> I need to generate the -irecode- function this way because, while I know
> how many groups there are to begin with (38), as I progressively pick
> individuals, the number of groups will diminish.
>
> The code is below.  There is nothing wrong with it as far as I know and
> it will work with a small number of groups, but with a large number of
> groups, the string length exceeds the 244 character limit.  So the comm
> macro ends up with only the first 244 characters of the command.
>
>
>
> * maxg is the total number of groups
> * prob is each person's probability
>
> local p = uniform()   /* generate a probability from U(0,1)  */
>
> local p0 = 0
>
> local comm = "irecode(`p', 0"
>
> /* The total number of groups is maxg
>   This loop calculates the total probability in each group,
>   adds it to the cumulative probability,
>   and appends it to the string stored in the comm local */
>
> forvalues i = 1/`maxg'  {
>        qui summ prob if picked==0 & group==`i'      /* sum of
> probabilities in a group  */
>        local pg`i' = r(sum)                         /* sum(prob) in
> group i  */
>        local k = `i'-1                              /* number of
> previous group */
>        local p`i' = `p`k'' + `pg`i''                /* add this sum to
> previous sum  */
>        local comm = "`comm'" + ", `p`i''"
> }
>
> local comm = "`comm'" + ")"
>
>
> Now I can get around this, I suppose, by getting rid of the comm macro
> altogether and instead using a series of -if- statements.
>
> if `maxg' == 38  {
> local group = irecode(`p',0,`p1',`p2',`p3', ...,`p38')
> }
> else if `maxg' == 37 {
> local group = irecode(`p',0,`p1',`p2',`p3', ...,`p37')
> }
> else if `maxg' == 36 {
> local group = irecode(`p',0,`p1',`p2',`p3', ...,`p36')
> }
> else if `maxg' == 35 {
> local group = irecode(`p',0,`p1',`p2',`p3', ...,`p35')
> }
> etc, etc
>
> But this is a tad inelegant.  Can anyone think of anything more
> efficient?
>
>
> Kieran
>
> ______________________________________________
> Kieran McCaul MPH PhD
> WA Centre for Health & Ageing (M573)
> University of Western Australia
> Level 6, Ainslie House
> 48 Murray St
> Perth 6000
> Phone: (08) 9224-2140
> Fax: (08) 9224 8009
> email: kamccaul@meddent.uwa.edu.au
> http://myprofile.cos.com/mccaul
> http://www.researcherid.com/rid/B-8751-2008
> ______________________________________________
> The fact that no one understands you doesn't make you an artist.
>

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