Huh. Very interesting. I haven't really worked with manipulating contrast matrices before, save to do a prior contrasts. Could you explain the matrix you laid out just a bit more so that I can generalize it to my case?
Chuck Cleland wrote: > > > One approach would be to use glht() in the multcomp package. You > need to work out how to formulate the matrix of coefficients that give > the desired contrasts. Here is an example using the warpbreaks data > frame: > > fm <- lm(breaks ~ tension*wool, data=warpbreaks) > > # names(coef(fm)) > # (Intercept) tensionM tensionH woolB tensionM:woolB tensionH:woolB > > cm <- rbind( > "A vs. B at L" = c(0, 0, 0,-1, 0, 0), > "A vs. B at M" = c(0, 0, 0,-1,-1, 0), > "A vs. B at H" = c(0, 0, 0,-1, 0,-1), > "M vs. L at A" = c(0, 1, 0, 0, 0, 0), > "M vs. H at A" = c(0, 1,-1, 0, 0, 0), > "L vs. H at A" = c(0, 0,-1, 0, 0, 0), > "M vs. L at B" = c(0, 1, 0, 0, 1, 0), > "M vs. H at B" = c(0, 1,-1, 0, 1,-1), > "L vs. H at B" = c(0, 0,-1, 0, 0,-1)) > > library(multcomp) > > summary(glht(fm, linfct = cm), test = adjusted(type="none")) > > Simultaneous Tests for General Linear Hypotheses > > Fit: lm(formula = breaks ~ tension * wool, data = warpbreaks) > > Linear Hypotheses: > Estimate Std. Error t value p value > A vs. B at L == 0 16.3333 5.1573 3.167 0.002677 ** > A vs. B at M == 0 -4.7778 5.1573 -0.926 0.358867 > A vs. B at H == 0 5.7778 5.1573 1.120 0.268156 > M vs. L at A == 0 -20.5556 5.1573 -3.986 0.000228 *** > M vs. H at A == 0 -0.5556 5.1573 -0.108 0.914665 > L vs. H at A == 0 20.0000 5.1573 3.878 0.000320 *** > M vs. L at B == 0 0.5556 5.1573 0.108 0.914665 > M vs. H at B == 0 10.0000 5.1573 1.939 0.058392 . > L vs. H at B == 0 9.4444 5.1573 1.831 0.073270 . > --- > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 > (Adjusted p values reported -- none method) > > > -- View this message in context: http://www.nabble.com/Asking%2C-are-simple-effects-different-from-0-tp15835552p15852362.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
