robustbase (version 0.1-2)

tolEllipsePlot: Tolerance Ellipse Plot

Description

Plots the 0.975 tolerance ellipse of the bivariate data set x. The ellipse is defined by those data points whose distance is equal to the squareroot of the 0.975 chisquare quantile with 2 degrees of freedom.

Usage

tolEllipsePlot(x, mcd = NULL, cutoff = NULL, id.n = NULL,
	       classic = FALSE, tol = 1e-07,
	       xlab = "", ylab = "",
               main = "Tolerance ellipse (97.5%)",
	       txt.leg = c("robust", "classical"),
	       col.leg = c("red", "blue"),
	       lty.leg = c("solid","dashed"))

Arguments

x

a two dimensional matrix or data frame.

mcd

an object similar to those of class "mcd", only its components center and cov will be used. If missing, the MCD will be computed (via covMcd()).

cutoff

Distance needed to flag data points outside the ellipse

id.n

number of observations to be identified by a label. If not supplied, the number of observations with distance larger than cutoff is used.

classic

whether to plot the classical distances too. Default is FALSE.

tol

tolerance to be used for computing the inverse, see solve. Defaults to tol = 1e-7.

xlab, ylab, main

passed to plot.default.

txt.leg, col.leg, lty.leg

character vectors of length 2 for the legend, only if used if class = TRUE.

See Also

ellipsoidhull and predict.ellipsoid from package cluster.

Examples

data(hbk)
hbk.x <- data.matrix(hbk[, 1:3])
mcd <- covMcd(hbk.x)       # compute mcd in advance
## must be a 2-dimensional data set: take the first two columns :
tolEllipsePlot(hbk.x[,1:2])