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Re: st: Replacing values within a matched study


From   Svend Juul <SJ@SOCI.AU.DK>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Replacing values within a matched study
Date   Wed, 28 May 2008 13:50:33 +0200

Nada wrote:

I'm having trouble putting my finger on the solution to what may 
be a simple problem. 

I have a matched case control dataset with patients who have had 
breast, colon or prostate cancer with 4 matched controls each and 
a matching variable (groupid).  My data looks like this:

id  groupid  breast  colon  prostate  control
1         1       1      .         .        .
2         1       .      .         .        1
3         1       .      .         .        1
4         1       .      .         .        1
.
89       40       .      1         .        .
90       40       .      .         .        1
91       40       .      .         .        1
etc 

What I'm trying to do is replace breast = 0 for each control, or 
colon= 0 for each control, so that my data would look like this:

id  groupid  breast  colon  prostate  control
1         1       1      .         .        .
2         1       0      .         .        1
3         1       0      .         .        1
4         1       0      .         .        1
.
89       40       .      1         .        .
90       40       .      0         .        1
91       40       .      0         .        1

================================================================

Try this:

     . sort groupid id
     . by groupid: egen bmax=max(breast)
     . by groupid: egen cmax=max(colon)
     . by groupid: egen pmax=max(prostate)
     . recode breast (.=0) if bmax==1
     . recode colon (.=0) if cmax==1
     . recode prostate (.=0) if pmax==1

     . list id-control , clean

       id   groupid   breast   colon   prostate   control
  1.    1         1        1       .          .         .
  2.    2         1        0       .          .         1
  3.    3         1        0       .          .         1
  4.    4         1        0       .          .         1
  5.   89        40        .       1          .         .
  6.   90        40        .       0          .         1
  7.   91        40        .       0          .         1

Hope this helps
Svend
__________________________________________

Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000  Aarhus C, Denmark
Phone:  +45 8942 6090
Home:   +45 8693 7796
Email:  sj@soci.au.dk
__________________________________________ 


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