For a covfm object containing 2 models, this function plots the
Mahalanobis distance from the first model on the y-axis and the
Mahalanobis distance from the second model on the x-axis.
ddPlot.covfm(x, level = 0.95, strip = "", id.n = 3, ...)a "covfm" object.
a single numeric value between 0 and 1 giving the chi-squared percent point used to compute the outlyingness threshold.
a character string printed in the “strip” at the top of the plot.
a single nonnegative integer specifying the number of extreme points to label in the plot.
additional arguments are passed to xyplot.
if the models can be compared then the plotted trellis object is
invisibly returned. Otherwise x is returned invisibly.