This function extracts the full covariance matrices from a mixed/hierarchical
linear model fit using lme
.
extract_design(b)
a fitted model object of class lme
.
A list of matrices is returned.
D
contains the covariance matrix of the random effects.
V
contains the covariance matrix of the response.
X
contains the fixed-effect model matrix.
Z
contains the random-effect model matrix.
This method has been adapted from the method
mgcv::extract.lme.cov
in the mgcv
package, written by Simon
N. Wood simon.wood@r-project.org.