[R-sig-eco] Multivariate repeated measures ANOVA w 2 bs factors

Wagner, Markus mwagner at ceh.ac.uk
Tue Jan 3 16:58:18 CET 2012


Hi Steve

The Anova function of the car package, written by John Fox, should be able to do this.

The following may be useful as it contains teaching materials for another stats course (for psychologists) using R, and in particular example R9 may point you into the right direction:

http://psych.wisc.edu/moore/R_Analysis_of_Variance_Handouts_html.html


Best wishes

Markus



-----Original Message-----
From: r-sig-ecology-bounces at r-project.org [mailto:r-sig-ecology-bounces at r-project.org] On Behalf Of Steve Brewer
Sent: 03 January 2012 14:09
To: r-sig-ecology at r-project.org
Subject: [R-sig-eco] Multivariate repeated measures ANOVA w 2 bs factors

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



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Dr. Markus Wagner
Plant Ecologist
NERC Centre for Ecology & Hydrology
Maclean Building
Crowmarsh Gifford, Wallingford
Oxon OX10 8BB
United Kingdom

Tel. 01491 692418
E-Mail: mwagner at ceh.ac.uk


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