[R-sig-ME] MCMCglmm bivariate with offset

[Walid Mawass]

Hello everyone,

I am working on a bivariate MCMCglmm model and I want to include an 
offset term for my second response variable. I already know that for the 
offset, i have to fix the coefficient to 1 through the prior but it is 
not working in my case. I have 4 fixed effects fitted for both response 
variables and the offset is fitted for the second one using 
/at.level(trait,2)/.

prior1 <- list(B=list(V=diag(5)*1e8, mu=rep(0,5)), R=list(V=diag(2), 
nu=3), G=list(G1=list(V=diag(2), nu=3),G2=list(V=diag(2), nu=3)))
prior1$B$mu[5]<- 1
prior1$B$V[5,5]<- 1e-8

is this the proper way to set the prior? or should the fixed effects 
matrix have different dimensions since my model is bivariate:

model_multi <- MCMCglmm(cbind(AFR, OffMortality)~trait-1 + trait:COEFPAR 
+ trait:I(COEFPAR*COEFPAR) + trait:TWIN + trait:YEARM+ 
at.level(trait,2):log(FERTILITY), random = 
~us(trait):animal+us(trait):MOTHERW, rcov = ~us(trait):units, data = 
IAC, pedigree = prunedPed, family = c("gaussian", "poisson"), nitt = 
3500000, burnin = 500000, thin = 3000, prior = prior1, verbose = FALSE, 
pr=TRUE)

Thank you in advance for any advice.

-- 
Walid Mawass

Ph.D. candidate in Cellular and Molecular Biology

Population Genetics Laboratory

University of Québec at Trois-Rivières
3351, boul. des Forges, C.P. 500
Trois-Rivières (Québec) G9A 5H7
Telephone: 819-376-5011 poste 3384


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