contrMat: Contrast Matrices

In multcomp: Simultaneous Inference in General Parametric Models

Contrast Matrices

Description

Computes contrast matrices for several multiple comparison procedures.

Usage

contrMat(n, type = c("Dunnett", "Tukey", "Sequen", "AVE", 
                     "Changepoint", "Williams", "Marcus", 
                     "McDermott", "UmbrellaWilliams", "GrandMean"), 
         base = 1)

Arguments

n	a (possibly named) vector of sample sizes for each group.
type	type of contrast.
base	an integer specifying which group is considered the baseline group for Dunnett contrasts.

Details

Computes the requested matrix of contrasts for comparisons of mean levels. The general concept and specific choices are discussed by \bibcitethothorn2008b and \bibcitetBretz+Hothorn+Westfall_2010.

Value

The matrix of contrasts with appropriate row names is returned.

References

\bibshow

*

Examples

 n <- c(10,20,30,40)
 names(n) <- paste("group", 1:4, sep="")
 contrMat(n)	# Dunnett is default
 contrMat(n, base = 2)	# use second level as baseline
 contrMat(n, type = "Tukey")
 contrMat(n, type = "Sequen")
 contrMat(n, type = "AVE")
 contrMat(n, type = "Changepoint")
 contrMat(n, type = "Williams")
 contrMat(n, type = "Marcus")
 contrMat(n, type = "McDermott")
 ### Umbrella-protected Williams contrasts, i.e. a sequence of 
 ### Williams-type contrasts with groups of higher order 
 ### stepwise omitted
 contrMat(n, type = "UmbrellaWilliams")
 ### comparison of each group with grand mean of all groups
 contrMat(n, type = "GrandMean")

multcomp documentation built on March 9, 2026, 5:08 p.m.