multcomp (version 0.4-8)

contrMat: Contrast Matrices

Description

Computes contrast matrices for several multiple comparision procedures.

Usage

contrMat(n, type=c("Dunnett", "Tukey", "Sequen", "AVE", 
                   "Changepoint", "Williams", "Marcus", 
                   "McDermott", "Tetrade"), nlevel = NULL, base = 1)
contr.Dunnett(n, base = 1, contrasts=TRUE)

Arguments

n

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

type

type of contrast.

nlevel

number of levels of two factors (for type="Tetrade" only).

contrasts

a logical indicating whether contrasts should be computed.

base

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

Value

• The matrix of contrasts with appropriate rownames is returned.

Details

Computes the requested matrix of contrasts.

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)
 a <- 2
 b <- 3
 names(n) <- paste("group", 1:4, sep="")
 contrMat(n)	# Dunnett is default
 contrMat(n, base=2)	# use second level as baseline
 contr.Dunnett(names(n))  # it Moore-Penrose Inverse
 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")
 contrMat(n, type="Tetrade", nlevel=c(a,b))