plot.rasch {ltm} | R Documentation |
Produces the Item Characteristic Curves for fitted rasch
objects.
## S3 method for class 'rasch': plot(x, items = NULL, legend = FALSE, cx = -3.4, cy = 0.9, ...)
x |
an object inheriting from class rasch . |
items |
a numeric vector denoting which items to plot; if NULL all items are plotted. |
legend |
logical; if TRUE a legend is printed. |
cx |
the x-coordinate to be passed to legend . |
cy |
the y-coordinate to be passed to legend . |
... |
extra graphical parameters to be passed to plot , lines and legend . |
Item characteristic curves (also known as item response functions) show how the probability of a positive response, in each item, increases with the values of the latent variable (ability).
Dimitris Rizopoulos dimitris.rizopoulos@med.kuleuven.be
## Item Characteristic Curves for the Wirs data; ## plot only items 1, 3 and 5: m <- rasch(Wirs) plot(m, items = c(1, 3, 5), lwd = 3, cex = 1.4) ## Item Characteristic Curves for the Lsat data; ## plot all items plus a legend m <- rasch(Lsat) plot(m, legend = TRUE, cx = 1.5, cy = 0.4, lwd = 3, cex = 1.4)