leveneTests: Levene Tests of Homogeneity of Variances In heplots: Visualizing Hypothesis Tests in Multivariate Linear Models

Description

This function extends `leveneTest` to a multivariate response setting. It performs the Levene test of homogeneity of variances for each of a set of response variables, and prints a compact summary.

Usage

 `1` ```leveneTests(y, group, center = median, ...) ```

Arguments

 `y` A data frame or matrix of numeric response variables in a multivariate linear model. `group` a vector or factor object giving the group for the corresponding elements of the rows of `y` `center` The name of a function to compute the center of each group; `mean` gives the original Levene's (1960) test; the default, `median`, provides a more robust test suggested by Brown and Forsythe (1974). `...` other arguments, passed to `leveneTest`

Value

An object of classes "anova" and "data.frame", with one observation for each response variable in `y`.

Michael Friendly

References

Levene, H. (1960). Robust Tests for Equality of Variances. In Olkin, I. et al. (Eds.), Contributions to Probability and Statistics: Essays in Honor of Harold Hotelling, Stanford University Press, 278-292.

Brown, M. B. & Forsythe, A. B. (1974). Robust Tests For Equality Of Variances Journal of the American Statistical Association, 69, 364-367.

`leveneTest`, `bartlettTests`
 ```1 2 3 4 5 6 7``` ```leveneTests(iris[,1:4], iris\$Species) # handle a 1-column response? leveneTests(iris[,1, drop=FALSE], iris\$Species) data(Skulls, package="heplots") leveneTests(Skulls[,-1], Skulls\$epoch) ```