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.
Value
The matrix of contrasts with appropriate row names is returned.
References
Frank Bretz, Torsten Hothorn and Peter Westfall (2010),
Multiple Comparisons Using R, CRC Press, Boca Raton.
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")
### 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")