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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: AW: RE: Evaluating a set of conditions |

Date |
Wed, 23 Jun 2010 13:59:44 +0100 |

Yes, if there are missings it's more complicated than my initial answer could suggest. (a == 1) & (((b == 1) + (c ==1) + (d == 1) + (e == 1)) >= 2) would seem to match the possibilities better. Nick n.j.cox@durham.ac.uk Martin Weiss The result does seem to differ much, though, from the one Thomas evidently wants - as expressed by his example: ************* clear* set obs 10000 set seed 12345 foreach var of newlist a b c d e{ gen byte `var'=runiform()<.5 replace `var'=. if runiform()<.15 } //NJC gen disease_true = a & (b + c + d + e >= 2) /* */ if !missing(a, b, c, d, e) //Thomas 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==. //Comparison compare disease_true disease as disease_true ==disease ************* Nick Cox I think you need to be clear whether missing means true, false or indeterminate as far as this is concerned. Setting aside missings, as a, b, c, d, e are Booleans (1 = true, 0 = false) then gen disease_true = a & (b + c + d + e >= 2) is one way to do it. If missings make the problem indeterminate then tack on ... if !missing(a, b, c, d, e) Nick n.j.cox@durham.ac.uk Thomas Speidel 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. * * 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/

**Follow-Ups**:**Re: st: RE: AW: RE: Evaluating a set of conditions***From:*Thomas Speidel <thomas@tmbx.com>

**References**:**st: Evaluating a set of conditions***From:*Thomas Speidel <thomas@tmbx.com>

**st: RE: Evaluating a set of conditions***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**st: AW: RE: Evaluating a set of conditions***From:*"Martin Weiss" <martin.weiss1@gmx.de>

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