leveneTest {car} | R Documentation |
Computes Levene's test for homogeneity of variance across groups.
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, ...)
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). |
returns an object meant to be printed showing the results of the test.
adapted from a response posted by Brian Ripley to the r-help email list.
John Fox jfox@mcmaster.ca; original generic version contributed by Derek Ogle
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.
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)