WrightMap Tutorial 2
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Plotting the items in different ways
Updated Fri 24-Apr-2020
Setup
We start by creating mock person and item estimates.
For the person proficiencies we create a single vector with 1000 values.
set.seed(2020) 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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