conquestr (version 1.4.5)

informationWrightMap: informationWrightMap

Description

Plots test information function, relative to ability density, and item locations.

Usage

informationWrightMap(
  myItems,
  myAbilities,
  type = "empirical",
  minTheta = NA,
  maxTheta = NA,
  stepTheta = NA,
  scaleInfo = 1,
  plotItemPoints = "deltadots"
)

Value

A ggplot2 object.

Arguments

myItems

A list of matricies describing item parameters.

myAbilities

A vector of person abilities on one dimension.

type

A character String. Should the test information be calculated empirically ("empirical" - default) or analytically using moments of distribution ("approx").

minTheta

The smallest value of ability PDF to plot.

maxTheta

The largest value of ability PDF to plot.

stepTheta

The increment to iterate over the ability PDF. Defaults to 0.01.

scaleInfo

A scaling factor to apply to the plot of tesr information. Because ability distribution is a PDF with area one, and a test information function has area L, this can make the plot more interpretable. Defaults to 1.

plotItemPoints

A character string indicating what item points should be plotted along the x-axis. similar to the histogram of item locations plotted on a Wrightmap. Can be "none", "deltadots", "thresholds".

Examples

myDeltaDots <- data.frame(
  id = c(1:10),
  itemid = paste0("item", 1:10),
  delta = rnorm(10)
)
MyTaus <- data.frame(
  id = c(2L, 10L),
  itemId = NA,
  step = c(1L, 1L),
  tau = rnorm(2)
)
myItemList <- makeItemList(deltaDot = myDeltaDots, tau = MyTaus)
myInfoPlot <- informationWrightMap(myItemList, rnorm(1000, 0, 1), minTheta=-5, maxTheta=5)