get.block.items.from.data: Extract Block Items from Forced-Choice Data

In ForceChoice: Forced-Choice Modeling Based on Item Response Theory and Cognitive Diagnostic Models

Extract Block Items from Forced-Choice Data

Description

Infers the item composition of each forced-choice block from a character data matrix. Each cell should encode the within-block item ordering (e.g. "2>1>3" for a rank-3 block). The function parses all non-missing cells per block and returns sorted, unique item indices.

This function is the recommended way to recover block.items when only character-rank data are available. It works for all forced-choice types ("RANK", "MOLE", "PICK") as long as every item appears at least once across persons.

Usage

get.block.items.from.data(data)

Arguments

data	An N \times B character matrix (or data frame) of forced-choice responses. Each entry encodes an item ordering using integer item indices separated by ">" (e.g. "3>1>2"). Missing values (NA) are permitted and skipped.

Details

The returned block.items list defines the block layout used by the other converters. If data has B columns, the result has B elements, and result element b belongs to data column b. Item labels are treated as global item indices; they are not recoded to local positions.

The function scans observed strings only. Therefore, for partial-response formats, it can only recover items that appear in the observed partial strings:

• For "RANK", a complete ranking normally contains every item in the block, so one valid row can be sufficient.

• For "MOLE", only most- and least-preferred items appear in each cell. An item that is never chosen as most or least cannot be recovered from data alone.

• For "PICK", only picked items appear. Items that are never picked cannot be recovered from data alone.

In those partial-response cases, pass a complete user-defined block.items list to the fitting or conversion function when the raw data do not mention every item.

Value

A list of length B. Each element is an integer vector of global item indices appearing in that block, sorted in ascending order.

See Also

get.block.items.from.data.FCDCM for the FCDCM (binary-pair) variant.

get.response.from.data to convert character data to an integer pattern-index matrix.

Examples

# 3 persons, 2 blocks.
# Block 1 contains items 1 and 2; block 2 contains items 3, 4, and 5.
dat <- data.frame(
  block.1 = c("1>2", "2>1", "1>2"),
  block.2 = c("3>4>5", "5>4>3", "4>3>5"),
  stringsAsFactors = FALSE
)
get.block.items.from.data(dat)

ForceChoice documentation built on Sept. 13, 2026, 1:06 a.m.