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From |
Nick Cox <njcoxstata@gmail.com> |

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

Subject |
Re: st: Loop to compare several variables within different timepoints |

Date |
Sun, 2 Feb 2014 11:34:19 +0000 |

My code makes no assumptions about the exact number of variables, so it would not change. Nick njcoxstata@gmail.com On 2 February 2014 11:29, Nikolaos Pandis <nikpandis@gmail.com> wrote: > I completely agree with your initial comment-this was more of an exercise. > How would the code change if we assume that the exact number of variables is 25? > Thank you, > > Nick > > On Sun, Feb 2, 2014 at 12:52 PM, Nick Cox <njcoxstata@gmail.com> wrote: >> Statistically, this sounds dubious and unsound: the tests are not >> independent and the shotgun approach raises questions about your >> interpretation of the resulting P-values. >> >> Focusing on the Stata question, which is of some wider interest: >> >> If your variables were just a1, a2, a3, ..., c1, c2, c3 you could go >> >> foreach v in a b c { >> signrank `v'1 = `v'2 >> signrank `v'3 = `v'2 >> } >> >> so this just raises the question of how to extend "a b c" to whatever >> stubs you have. Your description of variable names is too vague >> ("about 25 variables") to imply exact code, but this shows one trick: >> >> unab stubs : *1 >> local stubs : subinstr local stubs "1" "", all >> >> That would reduce (e.g.) >> >> a1 b1 c1 d1 e1 f1 g1 h1 i1 j1 >> >> to >> >> a b c d e f g h i j >> >> after which the code would be >> >> foreach v of local stubs { >> signrank `v'1 = `v'2 >> signrank `v'3 = `v'2 >> } >> >> Nick >> njcoxstata@gmail.com >> >> >> On 2 February 2014 10:38, Nikolaos Pandis <nikpandis@gmail.com> wrote: >>> I have about 25 variables for which I recorded outcomes at 3 times >>> points (t1, t2, t3) >>> I would like to construct a loop where I can automate testing using >>> the "signrank" test >>> >>> I would like to do the following: >>> >>> signrank a1=a2 >>> signrank b1=b2 >>> signrank c1=c2 >>> ..... >>> signrank a3=a2 >>> signrank b3=b2 >>> signrank c3=c2 >>> .............. >>> >>> a,b,c are the variables and 1,2,3 refer to the timepoints >>> >>> I am only interested in 25*2=50 comparisons and not to compare >>> different letter variables between them. Only within the same >>> variables to compare between timepoints. >>> >> * >> * 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/ > * > * 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/ * * 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/

**Follow-Ups**:**Re: st: Loop to compare several variables within different timepoints***From:*Nikolaos Pandis <nikpandis@gmail.com>

**References**:**st: Loop to compare several variables within different timepoints***From:*Nikolaos Pandis <nikpandis@gmail.com>

**Re: st: Loop to compare several variables within different timepoints***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: Loop to compare several variables within different timepoints***From:*Nikolaos Pandis <nikpandis@gmail.com>

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