pairwise (version 0.4.4-5.1)

tff: Test information function

Description

plotting function for plotting the test information function (TIF).

Usage

tff(pair_obj, items = NULL, x = NULL,
  main = "Test Information Function", plot = TRUE, cat = FALSE,
  lwd = 2, col = 1, ...)

Arguments

pair_obj

an object of class "pair" as a result from function pair.

items

optional a vector (character or numeric) identifying the items (according their order in the data) to use for plotting the test information function.

x

The value(s) of the latent variable, at which the TIF will be evaluated. x should be either a numeric vector of theta values or a single numeric value. If x is given as a single numeric value plotting is supressed. If not given (default), 99 values spaced evenly between -4 and +4 will be used, handy for plotting.

main

see parameters for plot

plot

a logical (default plot = TRUE), defining wether to supress plotting an just return a matrix of the values of the Item information function.

cat

a logical (default cat = FALSE), defining wether to plot as an overlay to the Test information function the item category information functions based on item categories. If cat = TRUE and plot = FALSE the values of the item category information functions are returned.

lwd

see parameters for plot

col

see parameters for plot

...

arguments passed to plot

Value

a plot, a "data.frame" or a single numeric with values of the Test information function.

Details

no details in the moment.

Examples

# NOT RUN {
########
data(sim200x3)
result <- pair(sim200x3)
tff(pair_obj = result) # TIF plot 
tff(pair_obj = result, cat=TRUE) # TIF plot 
tff(pair_obj = result, items=c("V1","V3"), cat=TRUE) # TIF plot 
tff(pair_obj = result, x=0) # TIF at theta=0 
tff(pair_obj = result, x=seq(0,4,.1)) # TIF for a given range of Thetas
##### examples with other data ...
data(bfiN)
result <- pair(bfiN)
tff(pair_obj = result)
tff(pair_obj = result, cat=TRUE) # TIF plot 
# }