plot.irf {irtoys} | R Documentation |
Useful for plotting item response functions. The x
argument of
irf
should better be left out unless something special is required.
## S3 method for class 'irf': plot(x, add = FALSE, main = "Item response function", co = 1, label = FALSE, ...)
x |
An object produced by function irf |
add |
When add=T , the IRF is added to a plot, otherwise a new plot is started. Default is F. |
main |
The main title of the plot, given that add=F . |
co |
The colour of the IRF curve. Default is 1 for black. Use co=NA to plot each IRF in a different colour. |
label |
When label=T , individual curves will be labeled with the item number. |
... |
Any additional plotting parameters |
Ivailo Partchev
data(Scored) p.2pl <- est(Scored, model="2PL", engine="ltm") # plot IRF for all items in red, label with item number plot(irf(p.2pl), co="red", label=TRUE) # plot IRF for items 2, 3, and 7 in different colours plot(irf(p.2pl[c(2,3,7),]), co=NA)