If given two continuous variables, the variables are both scaled to
mean 0 and variance 1. Then the returned value is the ratio of the area of
the convex hull of the data to the area obtained from the product of the
ranges of the two areas, i.e. the area of the bounding rectangle.
If given two categorical variables, all combinations are tabulated. The
returned value is the number of non-zero table entries divided by the total
number of table entries.
If given one categorical and one continuous variable, the returned value is
the weighted mean of the range of the continuous variable within each
category divided by the overall range of the continuous variable, where the
weights are given by the number of observations in each level of the
categorical variable.
Requires package scagnostics
if a scagnostics measure is specified
in method
. Requires package hdrcde
if "DECR"
(density
estimate confidence region) is specified in method
. These only apply
to cases where x
and y
are both numeric.