Kevin, I guess this may not have a one line solution (I may be wrong). I would try something like this: -Get all the unique (use 'unique') values in 'temp' -Loop through these values and extract the subset of data and perform the ANOVA on this subset.
As an example, code may go something like this: X<-data.frame(temp=c(12,12,12,12,12,14,14,12,14,14,14,14), day=c('LD','LD','SD','LD','SD','SD','LD','SD','LD','LD','SD','SD'), var=rnorm(12)) temp_unique <- unique(X$temp) for (i in seq(temp_unique)){ Y <- X[X$temp==temp_unique[i],] # perform ANOVA here on Y } You may have to append the ANOVA results to another variable to retrieve them. Do the same for 'line' too. -Ashoka. --- Scientist Pacific Northwest National Laboratory Richland, WA On Dec 13, 2007 12:21 PM, Kevin J Emerson <[EMAIL PROTECTED]> wrote: > Hello R help-ers, > > > I have a basic question, but I have been playing with it for a while and > haven't quite gotten a hang of how to get it working. I want to perform > multiple one-way ANOVAs on subsets of data and am not sure how to do it in > an automated way. I am thinking of doing something similar to 'aggregate' > but I would like to collect all of the ANOVA results in a way in which I > can > get to the information from each of the independent ANOVAs. In effect, I > would like a data frame with each of the subset identifiers, F and P > values > in the rows. Or a list of all of the ANOVA summaries or something like > that. > > > > I would like to do an anova of the form aov(var ~ day) for each subset of > data corresponding to "temp" and "line". I have lots of temps and lines > and > would like to do this in an automated fashion. I know of the aggregate > function for doing this kind of thing to compute means etc, but I am not > sure how to call an anova in this way. I have looked at "by" and "apply" > and have tried various things but am unable to get it to work. > > > > Any help would be greatly appreciated. A sample of the dataset is below. > > > > Thank you for your time, > > Kevin > > > > > > temp line day var > > 12 WMG 1 LD 70.59 > > 12 WMG 1 LD 100.00 > > 12 WMG 1 LD 100.00 > > 12 WMG 1 SD 85.00 > > 12 WMG 1 SD 75.00 > > 12 WMG 1 SD 90.00 > > 12 WMG 2 LD 100.00 > > 12 WMG 2 LD 83.33 > > 12 WMG 2 LD 100.00 > > 12 WMG 2 SD 91.67 > > 14 WMG 1 LD 76.03 > > . > > > > > > > > > [[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. > -- --- Scientist Pacific Northwest National Laboratory Richland, WA [[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.