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Re: st: RE: RE: RE: RE: Combining multiple observations by an ID variable


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: RE: RE: Combining multiple observations by an ID variable
Date   Wed, 13 Jun 2012 01:29:15 +0100

Your original data structure strikes me as far better for the majority
of purposes for which it might be used within Stata. Whether -reshape
wide- is possible is thus secondary. It is almost certainly not a good
idea.

Incidentally, -reshape- is a command, not a function. Also, I see no
reason why the correct -merge- command should create extra
observations as you imply here.

Nick

On Tue, Jun 12, 2012 at 11:31 PM, Claude Beaty <cbeaty1@jhmi.edu> wrote:

> Reshape was something I considered as well. Unfortunately, every time I attempt to run this code I get the error "too many macros". I have stata 12, which I believe is the most updated version. If anyone knows of a way around this, please let me know.

Swanquist, Quinn Thomas

> Fair enough,
>
> If you need the observations to equal the number of visits and you need to keep the data from each visit, you are going to need to use the reshape wide function on the master dataset before the merge. Since you said that you have 70 variables for each visit, you will now have 70 * the max number of visits variables. Depending on your version of Stata you may or may not be able to work with that many variables.
>
> You can get help with this function using:
>
> help reshape

Claude Beaty

> It looks like the merger attempt was likely successful, though I'm sure there are some duplicates. However, your suggested code did not help to shift the data so that the total observations equal the number of ID codes instead of the number of visits. I have tried reshaping etc, but there are too many macros to reshape all of the variables. Is there another way? If I can arrange the data in this way, it is easier to compare with my previous file and find duplicate ID codes. As it stands now, it is difficult to tell if duplicate ID codes are due to successive visits or duplications created by the file merger.

Swanquist, Quinn Thomas

> Do you have an identifier for visit number (if not you could use date).
>
> Sort as follows:
>
> sort IDcode visit
>
> then merge many to one as follows:
>
> merge m:1 IDcode using "usingfile"

Claude Beaty

> I have a large dataset of observations in which individuals (~40,000 ID codes) were evaluated multiple times (5-10 visit numbers per individual) on over 70 variables. However, the data has been arranged so that each visit number is an observation, instead of each individual ID code as an observation. I need to merge this file with another file sorted by individual ID codes. How do I rearrange this data so that it is arranged by ID codes with consecutive follow up visits? Thanks

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