rICC: Function for producing theoretical and empirical item...

In mixRasch: Mixture Rasch Models with JMLE

Description

This function produces item characteristic curves for the family of Rasch models.

Usage

rICC(delt, theta, itemVector, xlim, ylim, plotTitle, xlab, ylab, 
     col = c("black","white"), colTheme, expectedScore=FALSE, 
     empICC=FALSE, empOnly=FALSE, gDevice, file, ...)

Arguments

delt	The threshold difficulties from a dichotomous or polytomous Rasch model.
theta	The estimated theta values associated with the analysis and paired with itemVector, only required when requesting an empirical ICC.
itemVector	The observed item responses, only required when requesting an empirical ICC.
xlim	A vector overriding default limits for the x axis.
ylim	A vector overriding default limits for the y axis.
plotTitle	Controls the main plot title.
xlab	The label for the x axis.
ylab	The label for the y axis.
col	A vector of the colors to be used in the plot. The first color will be used for item labels. The second color will be used for shading the area of rejection.
colTheme	Four color themes ("cavaliers", "dukes", "spartans", "greys") are provided. If you provide a color theme, it will override the col paramater.
expectedScore	Flag indicating whether polytomous items are presented as category probabilities (FALSE) or expected item scores (TRUE). Will be set to TRUE when requesting empirical ICC.
empICC	Flag indicating whether an empirical ICC should also be produced.
empOnly	A flag indicating if ONLY the empirical ICC should be produced.
gDevice	Controls graphics device. Options are "screen" (default), "jpg", or "png".
file	The name of the output file if a device other than "screen" is chosen.
...	Additional parameters passed to the plot command.

Details

The function produces an item characterisic curce plots. Both empirical and theoretical ICCs can be produced.

Author(s)

John T. Willse

Examples

library(mixRasch)
# Example data included with mixRasch
data(exRasch)

rasch1 <- mixRasch(exRasch,1,50, conv.crit=.0001, n.c=1)

# ICC for item 1
rICC(rasch1$item.par$delta[,1], rasch1$person.par$theta, 
     exRasch[,1], empICC=TRUE, colTheme="cavaliers")

mixRasch documentation built on May 2, 2019, 1:09 p.m.