leveneTest: Levene's Test

In jonathon-love/car: Companion to Applied Regression

Description

Computes Levene's test for homogeneity of variance across groups.

Usage

leveneTest(y, ...)
## S3 method for class 'formula'
leveneTest(y, data, ...)
## S3 method for class 'lm'
leveneTest(y, ...)
## Default S3 method:
leveneTest(y, group, center=median, ...)

Arguments

y	response variable for the default method, or a lm or formula object. If y is a linear-model object or a formula, the variables on the right-hand-side of the model must all be factors and must be completely crossed.
group	factor defining groups.
center	The name of a function to compute the center of each group; mean gives the original Levene's test; the default, median, provides a more robust test.
data	a data frame for evaluating the formula.
...	arguments to be passed down, e.g., data for the formula and lm methods; can also be used to pass arguments to the function given by center (e.g., center=mean and trim=0.1 specify the 10% trimmed mean).

Value

returns an object meant to be printed showing the results of the test.

Note

adapted from a response posted by Brian Ripley to the r-help email list.

Author(s)

John Fox [e-mail]; original generic version contributed by Derek Ogle

References

Fox, J. (2008) Applied Regression Analysis and Generalized Linear Models, Second Edition. Sage.

Fox, J. and Weisberg, S. (2011) An R Companion to Applied Regression, Second Edition, Sage.

Examples

with(Moore, leveneTest(conformity, fcategory))
with(Moore, leveneTest(conformity, interaction(fcategory, partner.status)))
leveneTest(conformity ~ fcategory*partner.status, data=Moore)
leveneTest(lm(conformity ~ fcategory*partner.status, data=Moore))
leveneTest(conformity ~ fcategory*partner.status, data=Moore, center=mean)
leveneTest(conformity ~ fcategory*partner.status, data=Moore, center=mean, trim=0.1)

jonathon-love/car documentation built on May 19, 2019, 7:28 p.m.