Fabricius Domingos <fabriciusm <at> gmail.com> writes: > > Hello, > > I am trying to obtain f-values for response (independent) variables from a > CCA performed in vegan package, to see which ones of them have > significative influence in my dependent variables (like the manual selection > in canoco), but I can't find any function (or package) that do such a thing. > The dependents variables are species data, and the independents are > ambiental data. > > Than you. > Dear Fabricius Domingos,
Use add1/drop1 for the vegan object with argument test = "permutation". For adding constraints, you need a 'scope' of variables considered for adding to the model. The following example shows how to do this with vegan package and one of its standard data sets: > library(vegan) > data(mite) > data(mite.env) > mbig <- cca(mite ~ ., mite.env) > m0 <- cca(mite ~ 1, mite.env) > add1(m0, scope = formula(mbig), test="perm") > m0 <- update(m0, . ~ . + Topo) > add1(m0, scope = formula(mbig), test="perm") > m0 <- update(m0, . ~ . + WatrCont) You can also see if some of the included variables should be dropped: > drop1(m0, test="perm") The usage of add1.cca is explained on its help page (see ?add1.cca). Cheers, Jari Oksanen ______________________________________________ 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.
