icrfPN {lazy.irt} R Documentation

## Calculation of Item Response Function of Partial Credit Items in Nominal Model Format

### Description

Calculation of Item Response Function of Partial Credit Items
in Nominal Model Format

### Usage

```icrfPN(paramPN, theta, smallP = 0, print = 0, plot = 0, debug = 0)
```

### Arguments

 `paramPN` Item Parameter Data Frame of Partial Credit Items in Nominal format `theta` Discrete theta values `smallP` Minimum value of probability `print` = 1 to print result `plot` = 1 to plot result `debug` = 1 to print intemediate result

### Details

An Example of Item Parameter datastet: maxncat = 5
Note that the subscript of the b-parameter ranges between
1 and ncat-1 (= maxscore) (We set c0=0.)

ncat A b1 b2 b3 b4

Item1 2 1.0 0.0 . . .
Item2 2 1.0 0.0 . . .
Item3 3 1.5 -1.0 0.0 . .
Item4 4 1.5 -1.0 0.0 1.0 .
Item5 5 1.5 -1.0 0.0 1.0 2.0

ICRF of category k of item j at theta, namely, p_{jk}(theta)
is defined as
p_{jk}(theta) = Ez_{jk}(theta) / sum_{k=0}^{ncat[j]-1} Ez_{jk}(theta)
where
Ez_{jk}(theta) = exp( 1.7 z_{jk}(theta) )
and
z_{jk}(theta) = a_j k (theta - b_{k}), k=0,1, ..., ncat[j]-1
with b_{j0}=0.

### Value

A list of:
P length(theta) x sum(ncat) icrf matrix
PP length(theta) x sum(ncat) icbf matrix
Pt length(theta) x nitems item response function

[Package lazy.irt version 0.1.3 Index]