draw.tetra {psych} | R Documentation |
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.
draw.tetra(r, t1, t2,shade=TRUE)
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) |
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.
William Revelle
tetrachoric
to find tetrachoric correlations, irt.fa
and fa.poly
to use them in factor analyses, scatter.hist
to show correlations and histograms.
if(require(mvtnorm)) { draw.tetra(.5,1,1) draw.tetra(.8,2,1)} else {print("draw.tetra requires the mvtnorm package")}