Biplot of the first two residual components

Item loadings on the first two residual principal components – the pair that usually carries any interpretable second dimension – plotted against one another on equal (isometric) axes. Items far from the origin with opposing signs on PC1 mark a possible contrast, and PC2 separates them further. Point colour follows the sign of the PC1 loading, the split the unidimensionality t-test uses by default.

Usage

plot_pca_biplot(fit)

Arguments

fit

A fitted object from rasch.

Value

Called for its plotting side effect; invisibly NULL.

Examples

set.seed(1)
d <- seq(-2, 2, length.out = 8)
X <- matrix(rbinom(500 * 8, 1, plogis(outer(rnorm(500), d, "-"))), 500, 8)
colnames(X) <- paste0("I", 1:8)
plot_pca_biplot(rasch(X))