Ellipses, Data Ellipses, and Confidence Ellipses

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Description

This function draws econfidence ellipses for covariance and correlation matrices derived from from either a matrix or dataframe.

Usage

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ellipse.mvdalab(data, center = c(0, 0), radius = "chi", scale = TRUE, segments = 51, 
        level = c(.95, .99), plot.points = FALSE, ...)

Arguments

data

A dataframe

center

2-element vector with coordinates of center of ellipse.

radius

Use of the Chi or F Distributions for setting the radius of the confidence ellipse

scale

use correlation or covariance matrix

segments

number of line-segments used to draw ellipse.

level

draw elliptical contours at these (normal) probability or confidence levels.

plot.points

Should the points be added to the graph.

...

additional arguments. Currently ignored.

Details

ellipse uses the singular value decomposition in order to generate the desired confidence regions. The default confidence ellipse is based on the chisquare statistic.

Value

Returns a graph with the ellipses at the stated as levels, as well as the ellipse coordinates.

Author(s)

Nelson Lee Afanador (nelson.afanador@mvdalab.com)

References

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.

Examples

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data(iris)
ellipse.mvdalab(iris[, 1:2], plot.points = FALSE)
ellipse.mvdalab(iris[, 1:2], center = colMeans(iris[, 1:2]), plot.points = TRUE)

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