Hi, all:
I am using extract.lme.cov to extract the covariance matrix of lme. But
the results are not expected.
For example,
b <- lme(travel~1,Rail,~1|Rail)
The default correlation for lme is no correlation within groups.
>extract.lme.cov(b,Rail)
The part of covariance matrix looks like:
1 2 3 4 5 6
1 631.4778 615.3111 615.3111 0.0000 0.0000 0.0000
2 615.3111 631.4778 615.3111 0.0000 0.0000 0.0000
3 615.3111 615.3111 631.4778 0.0000 0.0000 0.0000
4 0.0000 0.0000 0.0000 631.4778 615.3111 615.3111
5 0.0000 0.0000 0.0000 615.3111 631.4778 615.3111
6 0.0000 0.0000 0.0000 615.3111 615.3111 631.4778
Where does the covariance come from? Maybe I'm missing sth here?
Thanks,
Hua Li
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