lme ModelsThe model object is fit to the data. Using
the fitted values of the parameters, nsim new data vectors from
this model are simulated. Both object and m2 are fit by
maximum likelihood (ML) and/or by restricted maximum likelihood (REML)
to each of the simulated data vectors.
# S3 method for lme
simulate(object, nsim = 1, seed = , m2,
method = c("REML", "ML"), niterEM = c(40, 200), useGen, ...)an object of class simulate.lme with components null and
alt. Each of these has components ML and/or REML
which are matrices. An attribute called seed contains
the seed that was used for the random number generator.
an object inheriting from class "lme", representing a fitted
linear mixed-effects model, or a list containing an lme model
specification. If given as a list, it should contain
components fixed, data, and random
with values suitable for a call to lme. This argument
defines the null model.
an "lme" object or a list, like object
containing a second lme model specification. This argument defines
the alternative model. If given as a list, only those parts of the
specification that change between model object and m2
need to be specified.
an optional integer that is passed to set.seed. Defaults to
a random integer.
an optional character array. If it includes
"REML" the models are fit by maximizing the restricted
log-likelihood. If it includes "ML" the log-likelihood is
maximized. Defaults to c("REML", "ML"), in which case both
methods are used.
an optional positive integer specifying the number of
simulations to perform. Defaults to 1. This has
changed. Previously the default was 1000.
an optional integer vector of length 2 giving the number of
iterations of the EM algorithm to apply when fitting the object
and m2 to each simulated set of data. Defaults to c(40,200).
an optional logical value. If TRUE, the nlminb
optimizer is used with numerical derivatives of the log-likelihood. If
FALSE, the nlm algorithm is used with an
analytic gradient. The default
depends on the "pdMat" classes used in object and m2:
if both are standard classes (see pdClasses) then
defaults to FALSE, otherwise defaults to TRUE.
optional additional arguments. None are used.
José Pinheiro and Douglas Bates bates@stat.wisc.edu
Pinheiro, J.C., and Bates, D.M. (2000) Mixed-Effects Models in S and S-PLUS, Springer.
lme, set.seed
orthSim <-
simulate.lme(list(fixed = distance ~ age, data = Orthodont,
random = ~ 1 | Subject), nsim = 200,
m2 = list(random = ~ age | Subject))
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