geepack (version 1.3.11.1)

fixed2Zcor: Construct zcor vector

Description

Construct zcor vector (of fixed correlations) from a fixed working correlation matrix, a specification of clusters and a specifcation of waves.

Usage

fixed2Zcor(cor.fixed, id, waves)

Value

A vector which can be passed as the zcor argument to geeglm.

Arguments

cor.fixed

Matrix

id

Clusters

waves

Vector giving the ordering of observations within clusters.

Author

Søren Højsgaard,

See Also

genZcor, geeglm

Examples

timeorder <- rep(1:5, 6)
tvar      <- timeorder + rnorm(length(timeorder))
idvar <- rep(1:6, each=5)
uuu   <- rep(rnorm(6), each=5)
yvar  <- 1 + 2*tvar + uuu + rnorm(length(tvar))
simdat <- data.frame(idvar, timeorder, tvar, yvar)
head(simdat,12)

simdatPerm <- simdat[sample(nrow(simdat)),]
simdatPerm <- simdatPerm[order(simdatPerm$idvar),]
head(simdatPerm)

cor.fixed <- matrix(c(1    , 0.5  , 0.25,  0.125, 0.125,
                      0.5  , 1    , 0.25,  0.125, 0.125,
                      0.25 , 0.25 , 1   ,  0.5  , 0.125,
                      0.125, 0.125, 0.5  , 1    , 0.125,
                      0.125, 0.125, 0.125, 0.125, 1     ), nrow=5, ncol=5)
cor.fixed

zcor <- fixed2Zcor(cor.fixed, id=simdatPerm$idvar, waves=simdatPerm$timeorder)
zcor

mod4 <- geeglm(yvar~tvar, id=idvar, data=simdatPerm, corstr="fixed", zcor=zcor)
mod4