Dear Paul,
The argument y is the response variable and group is a factor defining
groups (as ?levene.test says). If you have more than one factor, then you
can use interaction() to create from them a factor with levels given by the
product set of the levels of the individual factors. Here's an example
> library(car)
> data(Moore)
> attach(Moore)
> levene.test(conformity, interaction(fcategory, partner.status))
Levene's Test for Homogeneity of Variance
Df F value Pr(>F)
group 5 1.4694 0.2219
39
> levels(interaction(fcategory, partner.status))
[1] "high.high" "low.high" "medium.high" "high.low" "low.low"
[6] "medium.low"
> levels(fcategory)
[1] "high" "low" "medium"
> levels(partner.status)
[1] "high" "low"
I'll add a couple of examples to the help page.
I hope this helps,
John
--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox
--------------------------------
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Paul Smith
> Sent: Wednesday, August 02, 2006 5:33 AM
> To: r-help@stat.math.ethz.ch
> Subject: [R] Syntax of Levene's test
>
> Dear All
>
> I am trying to use Levene's test (of package car), but I do
> not understand quite well how to use it. '?levene.test' does
> not unfortunately provide any example. My data are in a data
> frame and correspond to 4 factors plus response. Could
> someone please give me an example about how to use the command
>
> levene.test(y, group)
>
> ?
>
> Thanks in advance,
>
> Paul
>
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