shape_df_fipc: Combine fixed and new item metadata for fixed-item parameter...

In irtQ: Unidimensional Item Response Theory Modeling

Combine fixed and new item metadata for fixed-item parameter calibration (FIPC)

Description

This function merges existing fixed-item metadata with automatically generated metadata for new items, producing a single data frame ordered by specified test positions, to facilitate fixed item parameter calibration using est_irt().

Usage

shape_df_fipc(x, fix.loc = NULL, item.id = NULL, cats, model)

Arguments

x	A data.frame of metadata for items whose parameters remain fixed (e.g., output from shape_df()).
fix.loc	An integer vector specifying the row positions in the final output where fixed items should be placed.
item.id	A character vector of IDs for new items whose parameters will be estimated.If NULL, default IDs (e.g., "V1", "V2", ...) are assigned automatically.
cats	An integer vector indicating the number of response categories for each new item; order must match item.id.
model	A character vector of IRT model names for each new item. Valid options for dichotomous items: "1PLM", "2PLM", "3PLM", "DRM"; for polytomous items: "GRM", "GPCM".

Details

To use this function, first prepare a metadata frame x containing only fixed items - either created by shape_df() or imported from external software (e.g., via bring.flexmirt()), which must include columns id, cats, model, and all relevant parameter columns (par.1, par.2, etc.). The fix.loc argument should then specify the exact row positions in the final test form where these fixed items should remain. The length of fix.loc must match the number of rows in x, and the order of positions in fix.loc determines where each fixed-item row is placed.

Next, provide information for the new items whose parameters will be estimated. Supply vectors for item.id, cats, and model matching the number of new items (equal to total form length minus length of fix.loc). If item.id is NULL, unique IDs are generated automatically.

Value

A data.frame containing combined metadata for all items (fixed and new), ordered by test position.

Author(s)

Hwanggyu Lim [e-mail]

See Also

shape_df()

Examples

## Import the flexMIRT parameter output file
prm_file <- system.file("extdata", "flexmirt_sample-prm.txt", package = "irtQ")
x_fixed <- bring.flexmirt(file = prm_file, "par")$Group1$full_df

## Define positions of fixed items in the test form
fixed_pos <- c(1:40, 43:57)

## Specify IDs, models, and category counts for new items
new_ids <- paste0("NI", 1:6)
new_models <- c("3PLM", "1PLM", "2PLM", "GRM", "GRM", "GPCM")
new_cats <- c(2, 2, 2, 4, 5, 6)

## Generate combined metadata for FIPC
shape_df_fipc(x = x_fixed, fix.loc = fixed_pos, item.id = new_ids,
  cats = new_cats, model = new_models)

irtQ documentation built on July 27, 2026, 9:08 a.m.