I am looking to combine all three" test information function" lines (one for each model) into one and the same graph. I have a data set of category 1-5 Likert responses in 400 rows in sets of 8 columns (one for each item). I have ran three IRT models on these sets using mirt package in R, and produced test info plots. I would like to combine IRT test info plots from three different (graded response) models, three lines, in one and the same grid.
plot(PFgrmodel29, type = 'info', xlim = c(-4, 4), ylim=c(0,85))
plot(PFgrmodel43, type = 'info', xlim = c(-4, 4), ylim=c(0,85))
plot(PFgrmodel57, type = 'info', xlim = c(-4, 4), ylim=c(0,85))
Example of test info plot:
How can I achieve this with mirt, lattice, ggplot2 or similar?