contrMat | R Documentation |

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")

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