[R-sig-eco] Adding covariates in (SE)TAR models

2012-10-22 Thread Peter Søgaard Jørgensen
Hi all, I'm curious what your recommendations would be for how best to add a covariate to a (Self-Exciting) Threshold AutoRegressive model in R. I've looked at both the "setar" function of the tsDyn-package and the "tar" function of the TSA-package, none of which, with my limited experience in run

Re: [R-sig-eco] betadisper() and variation in community change

2012-10-22 Thread Gavin Simpson
Anything where you are interested in the centroid moving in compositional space is handled by `adonis()` at least for testing if the change is significant. betadisper() handles the case when you want to know if the spread about the centroid is changing. Neither do what you want in total I don't t

Re: [R-sig-eco] betadisper() and variation in community change

2012-10-22 Thread Gustaf Granath
Thanks Gavin. Let me try to explain what Im trying to do. My data are hierarchically structured, I have subplots within sites and these subplots are measured over many years. I want to compare how vegetation composition varies over time at the site level (a bit like the example in Zuur 2007, p

[R-sig-eco] Cluster coefficients

2012-10-22 Thread Chris McOwen
Dear List, I am looking to cluster data, with the data being coefficients from a regression (subsets) The "NA" represent variables that were not present in the most likely model ( based on AIC), and the value the magnitude and direction of the relationship. I would like to cluster the data so

Re: [R-sig-eco] betadisper() and variation in community change

2012-10-22 Thread Gavin Simpson
betadisper() will give you a test of homogeneity of variance between groups; in other words it tests the null that the variance of the groups of sites does not change. adonis() is a test of location, which will test the null of no compositional change between groups of sites. Here I assume by group