Plot the Guttman scalogram

Displays the dichotomous Guttman-ordered response matrix as a heatmap (dark for a score of one), with persons sorted by location down the rows and items by location across the columns. The coefficient of reproducibility is shown in the subtitle.

Usage

plot_guttman(fit, max_persons = 80)

Arguments

fit

A fitted object from rasch.

max_persons

Persons are thinned to at most this many evenly spaced rows for legibility on large samples.

Value

Called for its plotting side effect; invisibly NULL.

Examples

set.seed(1)
d <- seq(-2, 2, length.out = 6)
X <- matrix(rbinom(200 * 6, 1, plogis(outer(rnorm(200), d, "-"))), 200, 6)
colnames(X) <- paste0("I", 1:6)
plot_guttman(rasch(X))