ellipses {psych}R Documentation

Plot data and 1 and 2 sigma correlation ellipses

Description

For teaching correlation, it is useful to draw ellipses around the mean to reflect the correlation. This variation of the ellipse function from John Fox's car package does so. Input may be either two vectors or a matrix or data.frame. In the latter cases, if the number of variables >2, then the ellipses are done in the pairs.panels function. Ellipses may be added to existing plots.

Usage

ellipses(x, y = NULL, add = FALSE, smooth=TRUE, lm=FALSE,data=TRUE, n = 2,span=2/3, iter=3, col = "red", xlab =NULL,ylab= NULL, ...)

Arguments

x a vector,matrix, or data.frame
y Optional second vector
add Should a new plot be created, or should it be added to?
smooth smooth = TRUE -> draw a loess fit
lm lm=TRUE -> draw the linear fit
data data=TRUE implies draw the data points
n Should 1 or 2 ellipses be drawn
span averaging window parameter for the lowess fit
iter iteration parameter for lowess
col color of ellipses (default is red
xlab label for the x axis
ylab label for the y axis
... Other parameters for plotting

Details

Ellipse dimensions are calculated from the correlation between the x and y variables and are scaled as sqrt(1+r) and sqrt(1-r).

Value

A single plot (for 2 vectors or data frames with fewer than 3 variables. Otherwise a call is made to pairs.panels.

Note

Adapted from John Fox's ellipse and data.ellipse functions.

Author(s)

William Revelle

References

Galton, Francis (1888), Co-relations and their measurement. Proceedings of the Royal Society. London Series, 45, 135-145.

See Also

pairs.panels

Examples

data(galton)
ellipses(galton,lm=TRUE)
ellipses(galton$parent,galton$child,xlab="Mid Parent Height",ylab="Child Height") #input are two vectors
data(sat.act)
ellipses(sat.act)  #shows the pairs.panels ellipses

[Package psych version 1.0-68 Index]