Thanks, that was the case. Thomas :-)
Peter Dalgaard schrieb: > Thomas Hoffmann <[EMAIL PROTECTED]> writes: > > >> Hi list-members >> >> can anybody tell me why >> >> > pairwise.t.test(val, fac) >> >> produces an empty p-table. As shown below: >> >> >> Pairwise comparisons using t tests with pooled SD >> >> data: val and fac >> >> AS AT Fhh Fm Fmk Fmu GBS Gf HFS Hn jAL Kol R_Fill >> AT - - - - - - - - - - - - - >> Fhh - - - - - - - - - - - - - >> Fm - - - - - - - - - - - - - >> Fmk - - - - - - - - - - - - - >> Fmu - - - - - - - - - - - - - >> GBS - - - - - - - - - - - - - >> Gf - - - - - - - - - - - - - >> HFS - - - - - - - - - - - - - >> Hn - - - - - - - - - - - - - >> jAL - - - - - - - - - - - - - >> Kol - - - - - - - - - - - - - >> R_Fill - - - - - - - - - - - - - >> Sa - - - - - - - - - - - - - >> >> However val and fac do have the same length and are not empty: >> > summary(fac) >> AS AT Fhh Fm Fmk Fmu GBS Gf HFS Hn >> jAL Kol R_Fill Sa >> 50 14 7 35 14 25 59 51 90 >> 65 12 26 96 26 >> > summary(val) >> Min. 1st Qu. Median Mean 3rd Qu. Max. NA's >> 0.0000 0.1744 0.6395 2.1540 1.7440 40.1200 223.0000 >> > > Does table(fac[!is.na(val)]) show any groups with 1 or less > observations? > > The construction > > s <- tapply(x, g, sd, na.rm = TRUE) > n <- tapply(!is.na(x), g, sum) > degf <- n - 1 > total.degf <- sum(degf) > pooled.sd <- sqrt(sum(s^2 * degf)/total.degf) > > is prone to give NA in such cases. > > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
