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From |
daniel klein <klein.daniel.81@googlemail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Looping a poisson regression analysis for levelsof a variable |

Date |
Fri, 12 Oct 2012 13:31:06 +0200 |

Tim, I did not fully understand what you are trying to do, but I hope my comments are helpful anyway. I guess your code fails to -restore-, because the -restore- command is in the worng place -- outside the loop/s (so is -preserve-). From what I understand, you want to -preserve- and -restore- the dataset repeatedly. To do this, the commands must be used inside the loop. However, using -preserve- and -restore- (repeatedly) is usually a very bad idea, because it is very slow. If you really need your variables to be coded 0 and 1, it might be faster to -generate- new variables satisfying this condition. Would something like this work for you? // get levels of period and age foreach x in period age { qui levelsof `x' ,l(`x') } // create dummy variables for each level of period foreach p of loc period { g byte p_`p' = (periode == `p') /// if inlist(period, 0, `p') & !mi(period) } // now run regerssions for each level of age foreach a of loc age { foreach p of loc period { cap noi : poisson st p_`p' if (age == `a') ,e(pyears) irr } } // drop the created variables // (alternatively you might want to create temporary variables // in the first place) drop p_? // given there are no other p_? variables in the dataset Best Daniel -- Dear all, I am running a Poisson regression on counts of surgery between two periods (Stata 11.2), however what I have is more than two periods in my data. Want I want to do is work out a loop that keeps the base period, but then cycles through the other periods. In this I have realized that my variable needs to be coded 0,1 or 1,2 etc, but my periods are 0,1,2,3,4. I cant 'keep' periods 0 and 2 as this returns incorrect IRRs. [...] levelsof period, local(levels) levelsof age, local(age) preserve foreach l of local levels { foreach a of local age { keep if period==0 | period==`l' tab period replace period = 1 if period==`l' cap nois: poisson st period if age==`a' & inlist(period, 0,`l'), exposure(pyears) irr } } restore * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

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