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Re: st: RE: repeated measures


From   Morten Hesse <mh@crf.au.dk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: repeated measures
Date   Wed, 08 Sep 2010 10:07:16 +0200

statalist dropped my first line

Should have been:
Is there any way to make "collapse" turn such a file with multiple observations into a panel.
If you have:

ID YEAR HOSPITALIZATION
1   1995  1
1   1997  1
1   1997  1
1   1998  1
2   1995  1

I.e. sometimes you have more than one observation, but sometimes you have zero. More than one is what "collapse" does. But zero?

And you want a panel with years nested within individuals, so that:

ID YEAR HOSPITALIZATION
1   1995  1
1   1996  0
1   1997  2
1   1998  1
2   1995  1
2   1996  0
2   1997  0
2   1998  0

I could not find a way to make collapse do this. When I used collapse, it omitted years with zero observations for an individual within that year. I did not specify cw, which I believe would omit observations with missing data, rather than missing observations.


Den 08-09-2010 09:52, Morten Hesse skrev:
that the file with multiple observations turn into a panel.
If you have:

ID YEAR HOSPITALIZATION
1   1995  1
1   1997  1
1   1997  1
1   1998  1
2   1995  1

I.e. sometimes you have more than one observation, but sometimes you have zero. More than one is what "collapse" does. But zero?

And you want a panel with years nested within individuals, so that:

ID YEAR HOSPITALIZATION
1   1995  1
1   1996  0
1   1997  2
1   1998  1
2   1995  1
2   1996  0
2   1997  0
2   1998  0

I could not find a way to make collapse do this. When I used collapse, it omitted years with zero observations for an individual within that year. I did not specify cw, which I believe would omit observations with missing data, rather than missing observations.

Best regards
Morten


Den 07-09-2010 22:36, Nick Cox skrev:
Excellent. He needs the dates as well, which is easy too.

Nick
n.j.cox@durham.ac.uk

David Bell

Or maybe simpler:

collapse (first) sbp dm glu, by(patient)

On Sep 7, 2010, at 4:07 PM, Nick Cox wrote:

The more difficult part of this is an FAQ, as at

FAQ . . . . . . . . . . . . . . . . . . . . . . . Replacing missing values
        2/03    How can I replace missing values with previous or
                following nonmissing values?
                http://www.stata.com/support/faqs/data/missing.html

The easier part of this is an application of -by()-, as at

SJ-2-1 pr0004 . . . . . . . . . . Speaking Stata: How to move step by: step Q1/02 SJ 2(1):86--102 (no commands)
        explains the use of the by varlist : construct to tackle
        a variety of problems with group structure, ranging from
        simple calculations for each of several groups to more
        advanced manipulations that use the built-in _n and _N

To copy lab results backward in time, try this

gen negvisitdate = - visitdate
bysort patient (negvisitdate) : replace sbp = sbp[_n-1] if missing(sbp)
bysort patient (negvisitdate) : replace dm = dm[_n-1] if missing(dm)
bysort patient (negvisitdate) : replace glu = glu[_n-1] if missing(glu)

Now

drop negvisitdate
bysort patient (visitdate) : keep if _n == 1

Alternatively, David Kantor has a utility -carryforward- at SSC. But something like the code here should suffice if your example is indicative.

Nick
n.j.cox@durham.ac.uk

Michael Eisenberg

I have a problem I hope you can help with that involves cleaning a
dataset for analysis.

I have a dataset with about 10K men.  Several men had multiple clinic
visits, so that there are about 12K observations.  There is also some
lab data that I'll need that was not obtained until follow up visits.

I would like to only analyze data from the earliest visit and the
first available lab data.

Can stata do this?


Turn this

patient     visitdate    sbp       dm          glu
1              1/1/09       140       .             .
1              1/4/09       128       .            202
1              2/1/09       131      1            .

2              4/1/09       160      .             341
2              4/4/09       144       .            180
2              5/1/09       170      1            .

3              6/1/09       119       .             .
3              6/4/09       107       .            .
3              7/1/09       124      .            96

4              9/1/09       104       1          110
4              9/4/09       155       .            .
4             10/1/09       .         .              .

Into this

patient     visitdate    sbp       dm          glu
1              1/1/09       140      1             202
2              4/1/09       160      1            341
3              6/1/09       119       .            96
3              9/1/09       104      1            110


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