informationWrightMap function

informationWrightMap

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

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

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".

Returns

A ggplot2 object.

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)