Uwe Ligges wrote: > > > Ingrid Tohver wrote: >> I would like to run a t-test within a "by" group function. My >> dataset, "error", is organized as the following (I have 133 Sites): >> >> Site week Dataset Region lat_map long_map mean_tsim diff20 diff40 >> diff80 >> ALFI 15 USACE UC 48.15625 -117.0938 8.87 1.34 1.90 >> 2.98 >> ALFI 16 USACE UC 48.15625 -117.0938 10.28 0.57 1.08 >> 2.27 >> ALFI 17 USACE UC 48.15625 -117.0938 11.08 0.74 1.30 >> 2.52 >> ALFI 18 USACE UC 48.15625 -117.0938 12.23 0.42 1.11 >> 2.42 >> ALFI 19 USACE UC 48.15625 -117.0938 13.19 1.00 1.73 >> 3.14 >> ALFI 20 USACE UC 48.15625 -117.0938 14.31 1.77 2.62 >> 3.78 >> >> I am interested in running the t-test by the "Site" index. My code >> looks like this: >> >> t_test<-by(error, error['Site'], function(dat) t.test(subset(error >> $diff20),subset(error$diff80), data=dat)) >> >> This code runs the t-test, but over the whole dataset without >> discriminating by Site, so each Site's result is the same. Could >> someone help determine a better approach or why mine is not working. > > I guess you want > > by(error, error['Site'], function(dat) t.test(dat$diff20, dat$diff40))
...and most likely also, paired=TRUE. Notice that the data= argument only works for the formula interface, which is not (yet) defined for paired data, but only for the y~group type two-sample case. > Uwe Ligges > > >> Thank you, >> Ingrid >> >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide >> http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalga...@biostat.ku.dk) FAX: (+45) 35327907 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
