Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
st: RE: Duplicate combinations of variables
From
"Nick Cox" <[email protected]>
To
<[email protected]>
Subject
st: RE: Duplicate combinations of variables
Date
Thu, 25 Mar 2010 15:19:06 -0000
Assuming that your identifiers are numeric, as implied here, then
gen minID = min(CaseID, ControlID)
gen maxID = max(CaseID, ControlID)
duplicates report minID maxID
and this check will do no harm:
assert CaseID != ControlID
For more on the min-max trick here, see e.g.
SJ-8-4 dm0043 . Tip 71: The problem of split identity, or how to group
dyads
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N.
J. Cox
Q4/08 SJ 8(4):588--591 (no
commands)
tip on how to handle dyadic identifiers
Nick
[email protected]
Miranda Kim
I am a Stata 11 user, and I wonder if anyone has advice on achieving the
following:
I have two variables, one with ID numbers for cases and one with ID
numbers for matched controls in a case control study. There are 3
controls matched to each case, and a subject may serve as a control for
more than one case or later become a case. I am wanting to check that in
my dataset all the pairs of cases and their matched control are unique;
ie that I don't have for example:
Case ID Control ID
123 253
253 123
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/