iif_fmp {flexmet}

FMP Item Information Function

Description

Find FMP item information for user-supplied item and person parameters.

Usage

iif_fmp(theta, bmat, maxncat = 2, cvec = NULL, dvec = NULL)

Arguments

theta

Vector of latent trait parameters.

bmat

Items x parameters matrix of FMP item parameters (or a vector of FMP item parameters for a single item).

maxncat

Maximum number of response categories (the first maxncat - 1 columns of bmat are intercepts).

cvec

Optional vector of lower asymptote parameters. If cvec = NULL, then all lower asymptotes set to 0.

dvec

Optional vector of upper asymptote parameters. If dvec = NULL, then all upper asymptotes set to 1.

Value

Matrix of item information.

Examples

# plot the IIF for a dichotomous item with k = 2

set.seed(2342)
bmat <- sim_bmat(n_items = 1, k = 2)$bmat

theta <- seq(-3, 3, by = .01)

information <- iif_fmp(theta = theta, bmat = bmat)

plot(theta, information, type = 'l')