multcomp (version 0.991-1)

contrMat: Contrast Matrices

Description

Computes contrast matrices for several multiple comparison procedures.

Usage

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

Arguments

n

a (possibly named) vector of sample sizes for each group or a vector of factor levels.

type

type of contrast.

base

an integer specifying which group is considered the baseline group for Dunnett contrasts.

Value

• The matrix of contrasts with appropriate row names is returned.

Details

Computes the requested matrix of contrasts for comparisons of mean levels.

References

Frank Bretz, Alan Genz and Ludwig A. Hothorn (2001), On the numerical availability of multiple comparison procedures. Biometrical Journal, 43(5), 645--656.

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")