Multivariate Linear Mixed Model in lme4

Question

I wonder how to fit multivariate linear mixed model with lme4. I fitted univariate linear mixed models with the following code:

library(lme4)
lmer.m         


        

Answer 1

This can sometimes be faked satisfactorily in nlme/lme4 by simply reformatting your data like

require(reshape)
Data = melt(data, id.vars=1:3, variable_name='Y')
Data$Y = factor(gsub('Y(.+)', '\\1', Data$Y))

> Data
  Block A B Y value
1     1 1 1 1 135.8
2     1 1 2 1 149.4
3     1 1 3 1 155.4
4     1 2 1 1 105.9
5     1 2 2 1 112.9
6     1 2 3 1 121.6
...

and then including the new variable Y in your linear mixed model.

However, for true Multivariate Generalized Linear Mixed Models (MGLMM), you will probably need the sabreR package or similar. There is also an entire book to accompany the package, Multivariate Generalized Linear Mixed Models Using R. If you have a proxy to a subscribing institution, you might even be able to download it for free from http://www.crcnetbase.com/isbn/9781439813270. I would refer you there for any further advice, as this is a meaty topic and I am very much a novice.

Answer 2

lmer and its elder sibling lme are inherently "one parameter left of ~". Have a look at the car packages; it offers no off-the shelf repeated measurement support, but you will find a few comments on the subject by searching the R list:

John Fox on car package

Answer 3

@John's answer above should be largely right. You add a dummy variable (ie--the factor variable Y) to the model. Here you have 3 subscripts i= 1...N for observations, j=1,...,4 for blocks, and h=1,2 for the dependent var. But you also need to force the level 1 error term to 0 (or to near zero), which I'm not sure lme4 does. Ben Bolker might provide more information. This is described more in Goldstein (2011) Chap 6 and Chap 7 for latent multivariate models.

IE

Y_hij = \beta_{01} z_{1ij} + \beta_{02} z_{2ij} + \beta X + u_{1j} z_{1ij} + u_{2j} z_{2ij}

So:

require(reshape2)
Data = melt(data, id.vars=1:3, variable_name='Y')
Data$Y = factor(gsub('Y(.+)', '\\1', Data$Y))

m1 <- lmer(value ~ Y + A*B + (1|Block) + (1|Block*A), data= Data)
# not sure how to set the level 1 variance to 0, @BenBolker
# also unclear to me if you're requesting Y*A*B instead of Y + A*B