Change polytomous items to dichotomous item format

Transforms a matrix of items into a new matrix where the select polytomous items have been converted into comparable dichotomous items with the same information.

Usage

poly2dich(data, which.items = 1:ncol(data), sep = "_cat.")

Arguments

data: an object of class data.frame or matrix
which.items: a vector indicating which items should be transformed into the dichotomous form. Default uses all input items
sep: character vector pattern to append to each item name in data

Value

Returns an integer matrix

References

Chalmers, R., P. (2012). mirt: A Multidimensional Item Response Theory Package for the R Environment. Journal of Statistical Software, 48(6), 1-29. doi:10.18637/jss.v048.i06

Author

Phil Chalmers rphilip.chalmers@gmail.com

Examples


if (FALSE) { # \dontrun{
data(Science)

head(Science)
newScience <- poly2dich(Science)
head(newScience)

newScience2 <- poly2dich(Science, which.items = 2)
head(newScience2)

} # }