plot.eirm {eirm}

Person-Item Map for Explanatory IRT Models

Description

This function creates a person-item map for an object returned from the eirm function. The function was modified from plotPImap in package eRm.

Usage

## S3 method for class 'eirm'
plot(
  x,
  difficulty = FALSE,
  sorted = TRUE,
  theta = NULL,
  main = "Person-Item Map",
  latdim = "Latent Dimension",
  pplabel = "Person\nParameter\nDistribution",
  cex.gen = 0.7,
  ...
)

Arguments

x

An object returned from the eirm function.

difficulty

Whether difficulty should be used instead of easiness (default: FALSE).

sorted

Whether the parameters should be sorted in the plot (default: TRUE).

theta

A vector of estimated theta values. If NULL, then theta values are obtained from the estimated eirm model. It might be better to save the theta values from a baseline model (e.g., Rasch) and use them when creating a person-item map.

main

Main title for the person-item map.

latdim

Label of the x-axis, i.e., the latent dimension.

pplabel

Title for the upper panel displaying the person parameter distribution.

cex.gen

A numerical value giving the amount by which plotting text and symbols should be magnified relative to the default. Here cex.gen applies to all text labels. The default is 0.7.

...

Other plot-related arguments.

Value

A person-item map.

Examples

data("VerbAgg")
mod0 <- eirm(formula = "r2 ~ -1 + situ + btype + (1|id)", data = VerbAgg)
plot(mod0)
plot(mod0, difficulty = TRUE) # Plot difficulty instead of easiness