# getME

##### Extract or Get Generalized Components from a Fitted Mixed Effects Model

Extract (or “get”) “components” -- in a
generalized sense -- from a fitted mixed-effects model,
i.e., (in this version of the package) from an object of
class `"'>merMod"`

.

- Keywords
- utilities

##### Usage

`getME(object, name, ...)`# S3 method for merMod
getME(object,
name = c("X", "Z", "Zt", "Ztlist", "mmList", "y", "mu", "u", "b",
"Gp", "Tp", "L", "Lambda", "Lambdat", "Lind", "Tlist",
"A", "RX", "RZX", "sigma", "flist",
"fixef", "beta", "theta", "ST", "REML", "is_REML",
"n_rtrms", "n_rfacs", "N", "n", "p", "q",
"p_i", "l_i", "q_i", "k", "m_i", "m",
"cnms", "devcomp", "offset", "lower", "devfun", "glmer.nb.theta"),
…)

##### Arguments

- object
a fitted mixed-effects model of class

`"'>merMod"`

, i.e., typically the result of`lmer()`

,`glmer()`

or`nlmer()`

.- name
a character vector specifying the name(s) of the “component”. If

`length(name) > 1`

or if`name = "ALL"`

, a named`list`

of components will be returned. Possible values are:`"X"`

:fixed-effects model matrix

`"Z"`

:random-effects model matrix

`"Zt"`

:transpose of random-effects model matrix. Note that the structure of

`Zt`

has changed since`lme4.0`

; to get a backward-compatible structure, use`do.call(Matrix::rBind,getME(.,"Ztlist"))`

`"Ztlist"`

:list of components of the transpose of the random-effects model matrix, separated by individual variance component

`"mmList"`

:list of raw model matrices associated with random effects terms

`"y"`

:response vector

`"mu"`

:conditional mean of the response

`"u"`

:conditional mode of the “spherical” random effects variable

`"b"`

:conditional mode of the random effects variable

`"Gp"`

:groups pointer vector. A pointer to the beginning of each group of random effects corresponding to the random-effects terms, beginning with 0 and including a final element giving the total number of random effects

`"Tp"`

:theta pointer vector. A pointer to the beginning of the theta sub-vectors corresponding to the random-effects terms, beginning with 0 and including a final element giving the number of thetas.

`"L"`

:sparse Cholesky factor of the penalized random-effects model.

`"Lambda"`

:relative covariance factor \(\Lambda\) of the random effects.

`"Lambdat"`

:transpose \(\Lambda'\) of \(\Lambda\) above.

`"Lind"`

:index vector for inserting elements of \(\theta\) into the nonzeros of \(\Lambda\).

`"Tlist"`

:vector of template matrices from which the blocks of \(\Lambda\) are generated.

`"A"`

:Scaled sparse model matrix (class

`"dgCMatrix"`

) for the unit, orthogonal random effects, \(U\), equal to`getME(.,"Zt") %*% getME(.,"Lambdat")`

`"RX"`

:Cholesky factor for the fixed-effects parameters

`"RZX"`

:cross-term in the full Cholesky factor

`"sigma"`

:residual standard error; note that

`sigma(object)`

is preferred.`"flist"`

:a list of the grouping variables (factors) involved in the random effect terms

`"fixef"`

:fixed-effects parameter estimates

`"beta"`

:fixed-effects parameter estimates (identical to the result of

`fixef`

, but without names)`"theta"`

:random-effects parameter estimates: these are parameterized as the relative Cholesky factors of each random effect term

`"ST"`

:A list of S and T factors in the TSST' Cholesky factorization of the relative variance matrices of the random effects associated with each random-effects term. The unit lower triangular matrix, \(T\), and the diagonal matrix, \(S\), for each term are stored as a single matrix with diagonal elements from \(S\) and off-diagonal elements from \(T\).

`"n_rtrms"`

:number of random-effects terms

`"n_rfacs"`

:number of distinct random-effects grouping factors

`"N"`

:number of rows of

`X`

`"n"`

:length of the response vector,

`y`

`"p"`

:number of columns of the fixed effects model matrix,

`X`

`"q"`

:number of columns of the random effects model matrix,

`Z`

`"p_i"`

:numbers of columns of the raw model matrices,

`mmList`

`"l_i"`

:numbers of levels of the grouping factors

`"q_i"`

:numbers of columns of the term-wise model matrices,

`ZtList`

`"k"`

:number of random effects terms

`"m_i"`

:numbers of covariance parameters in each term

`"m"`

:total number of covariance parameters

`"cnms"`

:the “component names”, a

`list`

.`"REML"`

:`0`

indicates the model was fitted by maximum likelihood, any other positive integer indicates fitting by restricted maximum likelihood`"is_REML"`

:same as the result of

`isREML(.)`

`"devcomp"`

:a list consisting of a named numeric vector,

`cmp`

, and a named integer vector,`dims`

, describing the fitted model. The elements of`cmp`

are:- ldL2
twice the log determinant of

`L`

- ldRX2
twice the log determinant of

`RX`

- wrss
weighted residual sum of squares

- ussq
squared length of

`u`

- pwrss
penalized weighted residual sum of squares, “wrss + ussq”

- drsum
sum of residual deviance (GLMMs only)

- REML
REML criterion at optimum (LMMs fit by REML only)

- dev
deviance criterion at optimum (models fit by ML only)

- sigmaML
ML estimate of residual standard deviation

- sigmaREML
REML estimate of residual standard deviation

- tolPwrss
tolerance for declaring convergence in the penalized iteratively weighted residual sum-of-squares (GLMMs only)

`dims`

are:- N
number of rows of

`X`

- n
length of

`y`

- p
number of columns of

`X`

- nmp
`n-p`

- nth
length of

`theta`

- q
number of columns of

`Z`

- nAGQ
see

`glmer`

- compDev
see

`glmerControl`

- useSc
`TRUE`

if model has a scale parameter- reTrms
number of random effects terms

- REML
`0`

indicates the model was fitted by maximum likelihood, any other positive integer indicates fitting by restricted maximum likelihood- GLMM
`TRUE`

if a GLMM- NLMM
`TRUE`

if an NLMM

`"offset"`

:model offset

`"lower"`

:lower bounds on model parameters (random effects parameters only).

`"devfun"`

:deviance function (so far only available for LMMs)

`"glmer.nb.theta"`

:negative binomial \(\theta\) parameter, only for

`glmer.nb`

.`"ALL"`

:get all of the above as a

`list`

.

%% -- keep at the very end:

- …
currently unused in lme4, potentially further arguments in methods.

##### Details

The goal is to provide “everything a user may
want” from a fitted `"merMod"`

object *as far*
as it is not available by methods, such as
`fixef`

, `ranef`

,
`vcov`

, etc.

##### Value

Unspecified, as very much depending on the `name`

.

##### See Also

`getCall()`

. More standard methods for `"merMod"`

objects, such as `ranef`

, `fixef`

,
`vcov`

, etc.: see `methods(class="merMod")`

##### Examples

```
# NOT RUN {
## shows many methods you should consider *before* using getME():
methods(class = "merMod")
(fm1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy))
Z <- getME(fm1, "Z")
stopifnot(is(Z, "CsparseMatrix"),
c(180,36) == dim(Z),
all.equal(fixef(fm1), b1 <- getME(fm1, "beta"),
check.attributes=FALSE, tolerance = 0))
## A way to get *all* getME()s :
## internal consistency check ensuring that all work:
parts <- getME(fm1, "ALL")
str(parts, max=2)
stopifnot(identical(Z, parts $ Z),
identical(b1, parts $ beta))
# }
```

*Documentation reproduced from package lme4, version 1.1-21, License: GPL (>= 2)*