R: Construct zcor vector

fixed2Zcor {geepack} | R Documentation

## 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)

### Arguments

`cor.fixed` | Matrix
`id` | Clusters
`waves` | Vector giving the ordering of observations within clusters.

### Value

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

### Author(s)

Søren Højsgaard, sorenh@math.aau.dk

### 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

[Package geepack version 1.3-0 Index]