> > Your line of code: > > zzz.aov <- aov(Intensity ~ Group + Error(Sample), data = zzzanova) > > indicates that you are trying to do a repeated measures ANOVA, not just an > ANOVA. The Error(Sample) term in your expression indicates that Sample is a > within subjects factor, which I presume is not the case. > The way I understood your data, the Sample column is just an id number for > the subjects - is that right? > > If you just want to compare the means of Intensity for the the four Groups, > then just do: > > zzz.aov <- aov(Intensity ~ Group, data = zzzanova) > > You may want to consult this resource for explicit examples of ANOVA in R: > > http://www.personality-project.org/R/r.anova.html > > Ravi Kulkarni
No, Error(Sample) does NOT indicate a repeated-measures ANOVA. This use of Error() is, in fact, correct for this between design, and labels the error partition, although not doing so will still return the same result with a generic name for the error partition. However, slightly more complicated designs (say, one between and one within factor) will *require* the Sample ID vector (as factor) to assign the partitions. [i.e., with s as the factor of IDs, and P as the repeated measure factor, and A as the between factor, then aov(dv~A*P+Error(s/P)) is the correct specification, although I prefer, and instruct my students, to expand explicitly in the aov call, what the call itself expands to: aov(dv~A+P+A:P+Error(s+s:P)), making it clear that there will be two partitions: s and s:P---s being used to test A, and s:P being used to test P and A:P]. -- Please avoid sending me Word or PowerPoint attachments. See <http://www.gnu.org/philosophy/no-word-attachments.html> ______________________________________________ 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.
