draw.tetra {psych}R Documentation

Draw a correlation ellipse and two normal curves to demonstrate tetrachoric correlation

Description

A graphic of a correlation ellipse divided into 4 regions based upon x and y cutpoints on two normal distributions. This is also an example of using the layout function.

Usage

draw.tetra(r, t1, t2,shade=TRUE)

Arguments

r

the underlying Pearson correlation defines the shape of the ellipse

t1

X is cut at tau

t2

Y is cut at Tau

shade

shade the diagram (default is TRUE)

Details

A graphic demonstration of the tetrachoric correlation. Used for teaching purposes. The default values are for a correlation of .5 with cuts at 1 and 1. Any other values are possible. The code is also a demonstration of how to use the layout function for complex graphics using base graphics.

Author(s)

William Revelle

See Also

tetrachoric to find tetrachoric correlations, irt.fa and fa.poly to use them in factor analyses, scatter.hist to show correlations and histograms.

Examples

if(require(mvtnorm)) {
draw.tetra(.5,1,1)
draw.tetra(.8,2,1)} else {print("draw.tetra requires the mvtnorm package")}

[Package psych version 1.4.5 Index]