[R] Mixed Models providing a correlation structure.

[Kevin Wright]

Why did you use the 'lower.tri' syntax?

Does this work for you?

lme(Y~Random, data = DATA,
random = list(Random = pdSymm(CovM,~Random)))

Kevin

On Wed, Jul 11, 2012 at 9:27 AM, Marcio <mresende at ufl.edu> wrote:
> Dear Simon,
> Thanks for the quick reply.
> Unfortunately I don't have access to Pinheiro and Bates. I tried googling
> the pdSymm and lme but I still cannot get the syntax right.
>
> In my model, I only have 1 random factor with repetitions (groups) (e.g. 2
> records per each level)
> I am pasting bellow a very small example (2 records and 2 levels) which
> demonstrates the error I am having.
> The syntax of lme is obviously wrong, and any help would be appreciated:
>
> Thanks
>
>> #Example
>> CovM <- matrix(c(1,0.5,0.5,1),2)
>> CovM
>      [,1] [,2]
> [1,]  1.0  0.5
> [2,]  0.5  1.0
>> DATA <- data.frame(Y = c(rnorm(4)), Random = c(1,1,2,2))
>> DATA
>             Y              Random
> 1  0.24037680      1
> 2  0.03477704      1
> 3 -1.83389279      2
> 4 -0.84793117      2
>> lme(Y~Random, data = DATA, random = list(Random = pdSymm
>> (CovM[lower.tri(CovM)],~Random)))
> Error in `Names<-.pdMat`(`*tmp*`, value = c("(Intercept)", "Random")) :
>   Length of names should be 1
>
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-- 
Kevin Wright