nlraa (version 1.2)

simulate_lme: Simulate values from an object of class lme

Description

Simulate values from an object of class lme. Unequal variances, as modeled using the ‘weights’ option are supported, and there is experimental code for considering the ‘correlation’ structure.

Usage

simulate_lme(
  object,
  nsim = 1,
  psim = 1,
  value = c("matrix", "data.frame"),
  data = NULL,
  ...
)

Value

It returns a vector with simulated values with length equal to the number of rows in the original data

Arguments

object

object of class lme or gls

nsim

number of samples, default 1

psim

parameter simulation level, 0: for fitted values, 1: for simulation from fixed parameters (assuming a fixed vcov matrix), 2: for simulation considering the uncertainty in the residual standard error (sigma), this returns data which will appear similar to the observed values. 3: in addition samples a new set of random effects.

value

whether to return a matrix (default) or an augmented data frame

data

the data argument is needed when using this function inside user defined functions.

...

additional arguments (it is possible to supply a newdata this way)

Details

This function is based on predict.lme function

It uses function mvrnorm to generate new values for the coefficients of the model using the Variance-Covariance matrix vcov. This variance-covariance matrix refers to the one for the parameters 'beta', not the one for the residuals.

See Also

predict.lme and ‘simulate.merMod’ in the ‘lme4’ package.

Examples

# \donttest{
require(nlme)
data(Orange)

fm1 <- lme(circumference ~ age, random = ~ 1 | Tree, data = Orange)

sims <- simulate_lme(fm1, nsim = 10)

# }