genItems {conquestr}  R Documentation 
genItems
Description
Generates a list of item parameter matrcies for use in
function like conquestr::genResponses
and conquestr::informationWrightMap
Usage
genItems(n, scores = NULL, deltadots, taus = NULL, discrims = 1)
Arguments
n 
How many items?

scores 
When NULL it is assumed that all items have
integer scoring, increasing for each category k, and begining from 0.
Otherwise a list where the elements are, in order:
a string naming a distribution function (for example runif , rnorm ) to generate random deviates
from (the scores).
a list of parameters to pass to the distribution function (for example, for runif , a list of
length 2 defining "min" and "max"). This list is assumed to be in order to be directly passed into
the function.
a boolean indicating whether the scores should be forced to be increasing accross the response
categories.
optionally a vector of item numbers to apply scores too. If not provided it is assumed that all items
will be scored.

deltadots 
A list where the elements are, in order:
a string naming a distribution function (for example runif , rnorm ) to generate random deviates
from (the delta dots).
a list of parameters to pass to the distribution function (for example, for runif , a list of
length 2 defining "min" and "max"). This list is assumed to be in order to be directly passed into
the function.

taus 
When NULL all items are assumed to be dichotomies.
Otherwise a list where the elements are, in order:
a string naming a distribution function (for example runif , rnorm ) to generate random deviates
from (the taus).
Or the string "manual" to indicate that a userdefined list of the tau paramters will be
provided.
a list of parameters to pass to the distribution function (for example, for runif , a list of
length 2 defining "min" and "max"). This list is assumed to be in order to be directly passed into
the function. if the first element in taus is "manual" this should be a list of taus to be used
this must be of the correct dimensions  for example, if there are 2 polytomous items being generated,
each with 3 response categories (k), then the list should be of length 2: 2 * (k 2) = 2 * (3  2) =
2 taus. This is because there are k1 taus per item, and the last tau is always constrained to be the negative
sum of the rest for identification purposes.
a Boolean indicating whether the taus should be forced to be increasing across the response
category boundaries (that is, enforce that no item exhibits disordered thresholds).
optionally a vector of item numbers to produce taus for. If not provided it is assumed that all items
are polytomous.
optionally a vector of response categories to apply to each item. For example if the user indicates that
5 items are polytomous, then a vector of length 5 where the first elements describes the count of response
categories for the first polytomous item, the second element describes the count of response
categories for the second polytomous item, and so on

discrims 
When NULL all items are assumed to have constant discrimination equal to 1.
Otherwise a list where the elements are, in order:
a string naming a distribution function (for example runif , rnorm ) to generate random deviates
from (the discriminations).
Or the string "manual" to indicate that a userdefined list of the discrimination paramters will be
provided.
a list of parameters to pass to the distribution function (for example, for runif , a list of
length 2 defining "min" and "max"). This list is assumed to be in order to be directly passed into
the function.
a Boolean indicating whether the discriminations are constant within items or whether each response category
within an item will have its own score should be forced to be increasing across the response
category boundaries (that is, this can be one way of specifying the Bock Nominal model).
optionally a vector of items to apply a unique discrimination to. Otherwise it is assumed that all items
have unique discriminations.

Value
A list of item matrices.
See Also
simplef()
, genResponses, browseVignettes("conquestr")
Examples
myItem < matrix(c(0, 0, 0, 0, 1, 1, 0, 1), ncol = 4, byrow = TRUE)
myItems < list(myItem, myItem)
myItems[[2]][2, 2] < 1 # make the second item delta equal to 1
myResponses < genResponses(rnorm(100), myItems)
[Package
conquestr version 1.0.7
Index]