RE: st: problem with forvalues loop

["Holly Heard" <hheard@rice.edu>]

That worked, thanks for the simple solution that I wish I had figured out
myself. And thanks for the shorter code to add 0 to my `s'. Best, HH

Holly E. Heard, Ph.D.
Senior Social Scientist
HERC Data Specialist
Houston Education Research Consortium, MS-28
Rice University
6100 Main Street
Houston, TX 77005
Phone: 713-348-3415
Fax: 713-348-5296


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Tuesday, February 25, 2014 10:49 AM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: problem with forvalues loop

Apart from advising -reshape long-, I recommend considering something like
this

forval s = 1/15
        local S : di %02.0f `s'
        gen retgrade`S'13 = .
        gen resc`S'13 = .

        forval y=1/10  {
             replace retgrade`S'13=retgrade`y' if resubj`y'==`s' &
rect`S'13==1
             replace resc`S'13=resc`y' if resubj`y'==`s' & rect`S'13==1
        .}
}


Nick
njcoxstata@gmail.com


On 25 February 2014 16:37, Holly Heard <hheard@rice.edu> wrote:
> Dear Statalisters (apologies for long post):
>
> I have data on exams that high school students take in 2013. Each 
> student can take more than one exam. The data were originally long 
> (one observation per exam), but I reshaped it wide, so that I have one 
> observation per student. Variables pertaining to each exam are 
> numbered 1 to 10, based on the maximum number of exams taken by a 
> student (most students took 3-4 exams, but one student took 10). There 
> are multiple variables based on each exam number: retgrade1-retgrade10 
> (grade student was in when took exam),
> resc1-resc10 (scale score of exam), etc. I need to reorganize and 
> rename variables based on the subject of the exam (algebra, reading, 
> etc.), which is denoted by resubj1-resubj10, which is the subject 
> category of the exam (1=Algebra I, 2=Algebra 2, 4=Chemistry). There 
> are 15 exam categories, although as noted, a maximum of 10 exams were
taken by any one student.
>
> I created a forvalues loop to go through each variable denoted by exam 
> number, and generate new variables based on subject number. My code is:
>
> forvalues y=1/10  {
>         forvalues s=1/15  {
>         if `s'<10 {
>          local s 0`s'
>         }
>         gen retgrade`s'13=retgrade`y' if resubj`y'==`s' & rect`s'13==1
>         gen resc`s'13=resc`y' if resubj`y'==`s' & rect`s'13==1
>         .
>
>         }
> }
>
> Here, y denotes exam number 1-10, and s denotes subject number 1-15. I 
> add
> 13 to the end of the new variables to denote the year of data 
> collection, and to distinguish new vars from old vars. It is possible 
> for a student to have taken an exam for a particular subject twice (if 
> they didn't pass the first time), so I create new variables only if 
> the student took the subject exam only once (rect`s'13==1).
>
> This loop runs many times, based on the many *(23851 missing values
> generated)* statements I get, but then I get the following error:
>
> retgrade0113 already defined
> r(110);
>
> So apparently the loop repeats itself at some point. I realize that y 
> and s are not fully nested (that would be too easy), but I'm not sure 
> how else to write the code to do what I want to do. I tried reversing 
> the order of the forvalues commands (y within s), but get the same 
> error. As far as I can tell, I should only have one retgrade0113 as 
> long as rect0113==1. Can anyone tell me what I'm doing wrong and how 
> to fix it? Thanks, Holly
>
> Holly E. Heard, Ph.D.
> Senior Social Scientist
> HERC Data Specialist
> Houston Education Research Consortium, MS-28 Rice University
> 6100 Main Street
> Houston, TX 77005
> Phone: 713-348-3415
> Fax: 713-348-5296
>
>
>
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