[R] specifying values in correlation matrix in nlme
Keyan Zhao
kzhao at usc.edu
Fri May 27 01:16:43 CEST 2005
Could anyone help with a linear mixed model fitting problem ?
The model is :
Y= Xp + Zu + e
where X, Z are known design matrix, p is fixed effect factor, u is
random effect, u~ (0, G) , e~(0,R)
The main problem is , I want to fix the covariance matrix G to be a
constant times a known covariance matrix A, G = c*A (c is positive
constant, A is a predefined matrix with values manually set by me.
I know the correlation option in lme function can specify some kind of
correlation. but only with the Construct function defined, not whatever
ever form I want.
Any good ideas of how to do this in R ?
Thanks a lot in advance,
Keyan Zhao
Computational Biology and Bioinformatics program
Univ of Southern California
Email: kzhao at usc.edu
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