R: Contrast Matrix for Constraints about the Mean

contrast {rmutil} | R Documentation

## Contrast Matrix for Constraints about the Mean

### Description

Return a matrix of contrasts for constraints about the mean.

### Usage

    contr.mean(n, contrasts = TRUE)

### Arguments

`n` | A vector of levels for a factor or the number of levels.
`contrasts` | A logical value indicating whether or not contrasts should be computed.

### Details

This function corrects `contr.sum` to display labels properly.

### Value

A matrix of computed contrasts with `n` rows and `k` columns, with `k=n-1` if `contrasts` is `TRUE` and `k=n` if `contrasts` is `FALSE`. The columns of the resulting matrices contain contrasts which can be used for coding a factor with `n` levels.

### See Also

`contrasts`, `C`, and `contr.sum`.

### Examples

    oldop <- options(contrasts=c("contr.sum","contra.poly"))
    y <- rnorm(30)
    x <- gl(3,10,labels=c("First","Second","Third"))
    glm(y~x)
    options(contrasts=c("contr.mean","contra.poly"))
    x <- gl(3,10,labels=c("First","Second","Third"))
    glm(y~x)
    options(oldop)

[Package rmutil version 1.1.3 Index]