Contrast Matrices
Computes contrast matrices for several multiple comparison procedures.
contrMat(n, type = c("Dunnett", "Tukey", "Sequen", "AVE",
"Changepoint", "Williams", "Marcus",
"McDermott", "UmbrellaWilliams", "GrandMean"),
base = 1)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. |
Computes the requested matrix of contrasts for comparisons of mean levels.
The matrix of contrasts with appropriate row names is returned.
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.
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")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.