WrightMap Tutorial 2

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Plotting the items in different ways

Updated Fri 24-Apr-2020


We start by creating mock person and item estimates.

For the person proficiencies we create a single vector with 1000 values.

mdim.sim.thetas <- matrix(rnorm(5000), ncol = 5)

Dealing with many, many items

What happens if you have too many items?

rasch2.sim.thresholds <- runif(50, -3, 3)

If we use the defaults…

wrightMap(rnorm(1000), rasch2.sim.thresholds)

Things do not look quite right.

Wright Map offers some options…

You can use the itemClassic or itemHist options for item.side.

wrightMap(rasch.sim.thetas, rasch2.sim.thresholds, item.side = itemClassic
    , item.prop = .5)

wrightMap(rasch.sim.thetas, rasch2.sim.thresholds, item.side = itemHist, item.prop = 0.5)

Or you can play with the way labels are presented:

wrightMap(rnorm(1000), rasch2.sim.thresholds, show.thr.lab = FALSE, label.items.srt = 45)

wrightMap(rnorm(1000), rasch2.sim.thresholds, show.thr.lab = FALSE, label.items.rows = 2)

wrightMap(rnorm(1000), rasch2.sim.thresholds, show.thr.lab = FALSE
    , label.items = c(1:50), label.items.rows = 3)

Or you can get rid of that axis completely

wrightMap(rnorm(1000), rasch2.sim.thresholds, show.thr.sym = FALSE
    , thr.lab.text = paste("I", 1:50, sep = ""), label.items = ""
    , label.items.ticks = FALSE)

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