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st: Evaluating a set of conditions


From   Thomas Speidel <thomas@tmbx.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Evaluating a set of conditions
Date   Tue, 22 Jun 2010 17:09:57 -0600

Following up on my previous post: http://www.stata.com/statalist/archive/2010-06/msg00984.html here is an example for something I am trying to achieve in a nice/efficient/eleganty way.

I have a number of dummies: a, b, c, d, e (missing values do exist)
Disease=true if the following conditions are met:

1) a must be true AND
2) any two of b, c, d, e are true

As I said missing values are crucial, especially when evaluating the second condition.

My current program works, but I don't think it is efficient and it probably does things that are unnecessary:

*******************************************
egen anytwo = rowtotal(a b c d e), missing
egen missing = rowmiss(a b c d e)
replace anytwo = . if (anytwo==0 & missing>=2 & missing<.)
replace anytwo = . if (anytwo==1 & missing==1)
replace anytwo = . if (anytwo==1 & missing==3)
replace anytwo = . if (missing>=4)

gen disease = 1 if (a==1 & anytwo>=2 & anytwo<.)
replace disease = 0 if (a==1 & anytwo<2)
replace disease = 0 if a==0
replace disease =. if a==.
*******************************************

I tried to play around with cond, but I found it was making this much more complicated then it is. I know I am complicating my life more than I need to which is why I am looking for alternative solutions.

--
Thomas Speidel


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