makeItemList {conquestr} R Documentation

## makeItemList

### Description

creates a list of matrices. Each matrix represent item parameters of the structure used in 'simplef' (a matrix of k categories by three (category score, delta dot, tau)).

### Usage

makeItemList(deltaDot, tau, scores = NULL)


### Arguments

 deltaDot a data frame or matrix of delta dots. If a data frame, column labels should be: "id", "itemid", "delta". "itemid" should be populated with an item label or be missing for all values. If a matrix, column order should be: "id", a unique item ID for each row; "itemid", item labels for each item (or NA); "delta", a delta dot. tau a data frame or matrix of taus for polytomous items. Only polytomous items should be in this file. If an item ID in 'deltaDot' in not in 'tau' it is assumed that the item is dichotomous. Where a polytomous item has k categories, there should be k-2 rows for that item in 'tau'. For example, a 3-category item has categories k_1, k_2, and k_3. There will be one value in 'tau' for this item. The tau parameters represent the deviation from the delta dot to give the item parameters for adjacent category boundaries (e.g., k_1 and k_2, and k_2 and k_3). The value in 'tau' represents the the first category boundary (e.g., k_1 and k_2). The second category boundary is constrained to be the negative sum of the other values of tau for that item. If a data frame, column labels should be "id", "itemid", "step", "tau". If a matrix, the column order should be: "id", a unique item ID for each item matched with values in 'deltaDot'; "itemid", item labels for each item (or NA); "step", an indicator of which step/item category this threshold represents (minimum value should be 1 and maximum value should be k-1); "tau" the value for the tau parameter associated with this step. scores a data frame of item response category scores. Not currently used - items are assumed to be scored as per the values in 'tau\$step'.

a list.

### Examples

nItems<- 10
id= seq(nItems),
itemId= NA,
delta = runif(nItems, -4, 1) # nItems items in range -4,1
)
myItemsTau<- data.frame(
id = NA,
itemId = NA,
step = NA,
tau = NA # this is only needed because the function is...in progress
)
myAbilities<- rnorm(100, 1, 2) # 100 person, offset from items - poor targeting (?)