polyserial function

Function for calculating polyserial correlations

This function calculates polyserial correlations using either an ad hoc or ML estimator.

polyserial(x, y, ml = TRUE)

Arguments

• x: A continuous variable.
• y: An ordinal variable with at least two categories.
• ml: A logical variable indicating whether to use a formal maximum likelihood estimator (default) or an ad hoc estimator.

Details

The variables should be numeric. The function returns NA is y has only one category.

Returns

Returns the polyserial correlation.

References

Olsson, U., Drasgow, F. & Dorans, N. J. (1982). The Polyserial Correlation Coefficient. Psychometika, 47, 337-347.

Author(s)

John T. Willse

Examples

x <- rnorm(500, 50,5)
y <- x + rnorm(500,0,2)
x <- x + rnorm(500,0,2)
cor(x,y)

y <- ifelse(y>50,1,0)

cor(x,y)

polyserial(x,y, ml=FALSE)
polyserial(x,y)