Dear Friends,

I am writing to seek any help on "lme" error message. I am using lme to do Mixed-model linear regression. I use my simulated data. However, sometimes, I get the following error message, which I do not understand. 

"Error in solve.default(pdMatrix(a, fact=TRUE)): system is computationally sigular"

I would appreciate any help about it.
Thanks a lot

Jingyuan Fu
Drs, Groningen Bioinformatics Center
the Netherlands
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