[R] MCMCglmm with cross-classified random effects

Dear R-users, I would like to fit a glmm with cross-classified random effects with the function MCMCglmm. Something along the lines: model1<-MCMCglmm(response~pred1, random=~re1+re2, data=data) where re1 and re2 should be crossed random effects. I was wondering whether you could tell me specify

[R] nlme Fixed Variance Function

Dear R users, I am trying to fit a gls model and weight my data points using a VarFixed structure. I have found many examples, but I do not understand the difference between the following models with varFixed specified in a different way: mod<-gls(y~x,weights=varFixed(~1/invsigma) mod<-gls(y~x,w