matrixLOR: Creating A Probability Matrix With Specified Local Odds...

Description Usage Arguments Details Value Warning Author(s) See Also Examples

View source: R/matrixLOR.R

Description

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

Usage

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Arguments

x

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

Details

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

Value

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

Warning

Caution is needed for local odds ratios close to zero.

Author(s)

Anestis Touloumis

See Also

nomLORgee and ordLORgee.

Examples

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

Example output

Loading required package: gnm
Loading required package: VGAM
Loading required package: stats4
Loading required package: splines
Call:
ordLORgee(formula = y ~ factor(trt) + factor(time) + factor(baseline), 
    data = arthritis, id = id, repeated = time, LORstr = "fixed", 
    LORterm = lorterm)

Number of clusters: 301 
Maximum cluster size: 3 

Number of categories: 5 
Number of observations: 888 

Coefficients:
           beta10            beta20            beta30            beta40 
    -1.8362948214      0.2693444384      2.2321986900      4.5280320442 
     factor(trt)2     factor(time)3     factor(time)5 factor(baseline)2 
    -0.5134738174     -0.0008047854     -0.3645328663     -0.6702606753 
factor(baseline)3 factor(baseline)4 factor(baseline)5 
    -1.2603788984     -2.6426918872     -3.9702756952 

Number of iterations: 6 
Algorithm converged: TRUE 

Local Odds Ratios Structure[1:6,1:6]
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    0    0    0    0    2    2
[2,]    0    0    0    0    2    2
[3,]    0    0    0    0    2    2
[4,]    0    0    0    0    2    2
[5,]    2    2    2    2    0    0
[6,]    2    2    2    2    0    0

pvalue of Null model: <0.0001 

multgee documentation built on July 12, 2017, 1:02 a.m.