Extracting model matrices used by lmer

Thank you very much, Ben, for your useful answer from long ago.
I still can't figure out a way to extract the Residual variance (sigma^2)
estimate using getME()?

Thanks again,
Asaf

On 15 November 2012 23:04, Ben Bolker <bbolker at gmail.com> wrote:

Asaf Weinstein <asafw.at.wharton at ...> writes:

Hello again,

Is there an easy way of obtaining the X and Z model matrices in

*y = X*Beta + Z*u + eps*

with the lmer function? I am trying to extract these because I want to
obtain maximum likelihood estimates for the case where sigma sq (error
variance) is known.

See

?getME

As shown in the examples:

   (nmME <- eval(formals(getME)$name))
 [1] "X"       "Z"       "Zt"      "u"       "Gp"      "L"       "Lambda"
 [8] "Lambdat" "A"       "flist"   "RX"      "RZX"     "beta"    "theta"
[15] "REML"    "n_rtrms" "is_REML"


so getME(model,"X") and getME(model,"Z") should do what you want.