Hey folks,

I am new to R and am trying to modify my multivariate eco-statistics course
by giving my students the option of doing all of the assignments in R.
Currently, all the assignments are done in either JMP, PC-Ord, or Primer.

One difficulty I'm having is figuring out how to do a multivariate repeated
measures ANOVA when there are two between-subjects factors. In other words,
I cannot figure out how to analyze a factorial experiment (clipping and
nutrient addition and their interaction) with three years of measurement of
shoot densities of a grass using a multivariate approach. I currently have
my students use JMP to do this and compare the results to univariate
approaches (I.e., assumed sphericity, G-G/H-F adjusted error df).

I have found examples using univariate approaches (e.g., using aov) and have
figured out how to use gls to address issues pertaining to the structure of
variance-covariance matrix. I have also found examples using multmodel and
Anova to do mv rm ANOVA in which there is a single between-subjects factor
and multiple time measurements. But I cannot find any examples of the latter
in which there are at least two between-subjects factors. Maybe the answer
is obvious, but my understanding of R is still very rudimentary.

Please understand that the purpose of this request is not necessarily to
find the best way to analyze the data, but to instruct students about the
use of a multivariate approach. If necessary, I could simplify the design,
but would prefer to keep the design I have, if possible.

Thanks,
Steve



J. Stephen Brewer 
Professor 
Department of Biology
PO Box 1848
 University of Mississippi
University, Mississippi 38677-1848
 Brewer web page - http://home.olemiss.edu/~jbrewer/
FAX - 662-915-5144 Phone - 662-915-1077



	[[alternative HTML version deleted]]

