[R-sig-eco] repeated measures with multivariate data

[Peter Solymos]

Kay,

using strata (restricting permutations within time points, and not
within locations) in adonis makes some sense, given that permutation
tests assume independence. But that does not solve the problem of
dependence, but it is a good starter. If you have a before-after
control-treatment design, you might want to use the absolute
difference between observations and do the adonis on the matrix of
differences (the dissimilarity then will represent distance in terms
of absolute deviation between time points). However, this won't show
the sign of the change, which might be of interest. If you have larger
number of repeated observations, the MARSS package is just appeared on
CRAN to fit multivariate autoregressive state-space models using a
Kalman-filter approach.

Cheers,

Peter

Péter Sólymos
Alberta Biodiversity Monitoring Institute
and Boreal Avian Modelling project
Department of Biological Sciences
CW 405, Biological Sciences Bldg
University of Alberta
Edmonton, Alberta, T6G 2E9, Canada
Phone: 780.492.8534
Fax: 780.492.7635
email <- paste("solymos", "ualberta.ca", sep = "@")
http://www.abmi.ca
http://sites.google.com/site/psolymos



On Fri, Jul 23, 2010 at 1:02 PM, Kay Cichini <Kay.Cichini at uibk.ac.at> wrote:
>
> dear list,
>
> i searched though the archives and the question of repeated measure analysis
> with species data was often brought up but, as far as i found, never clearly
> worked out.
>
> if i have, say two time points at wich i sampled replicated plots and thus
> had replicated paired mutivariate obervations, how to deal with them
> properly.
>
> if i used adonis, to restrict permutations on the pairs of plots (as this
> would be done in an univariate permutation test for paired observations)
> does not make sense to me but i'm also dubious about neglecting the
> dependence of the pairing.
>
> any ideas would be highly appreciated,
> kay
>
> -----
> ------------------------
> Kay Cichini
> Postgraduate student
> Institute of Botany
> Univ. of Innsbruck
> ------------------------
>
> --
> View this message in context: http://r-sig-ecology.471788.n2.nabble.com/repeated-measures-with-multivariate-data-tp5330819p5330819.html
> Sent from the r-sig-ecology mailing list archive at Nabble.com.
>
> _______________________________________________
> R-sig-ecology mailing list
> R-sig-ecology at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
>
>