multgee (version 1.9.0)

matrixLOR: Creating A Probability Matrix With Specified Local Odds Ratios

Description

Utility function to create a square probability matrix that satisfies the specified local odds ratios structure.

Usage

matrixLOR(x)

Value

Returns a square probability matrix that satisfies the local odds ratios structure defined by x.

Arguments

x

a square matrix with positive entries that describes the desired local odds ratios matrix.

Warning

Caution is needed for local odds ratios close to zero.

Author

Anestis Touloumis

Details

It is designed to ease the construction of the argument LORterm in the nomLORgee and ordLORgee functions.

See Also

nomLORgee and ordLORgee.

Examples

## Illustrating the construction of a "fixed" local odds ratios structure
## using the arthritis dataset. Here, we assume a uniform local odds ratios
## structure equal to 2 for each time pair.

## Create the uniform local odds ratios structure.
lorterm <- matrixLOR(matrix(2, 4, 4))

## Create the LORterm argument.
lorterm <- c(lorterm)
lorterm <- matrix(c(lorterm), 3, 25, TRUE)

## Fit the marginal model.
data(arthritis)
fitmod <- ordLORgee(y ~ factor(trt) + factor(time) + factor(baseline),
  data = arthritis, id = id, repeated = time, LORstr = "fixed",
  LORterm = lorterm)
fitmod