itempar_longitudinal_grmtree: Extract Item Parameters from Longitudinal GRM Tree

In grmtree: Recursive Partitioning for Graded Response Models

Extract Item Parameters from Longitudinal GRM Tree

Description

Extracts both discrimination and threshold parameters for each unique item from all terminal nodes, combining them into a single data frame with an average threshold column. Only T1 items are returned.

Usage

itempar_longitudinal_grmtree(object, node = NULL, clean_names = TRUE, ...)

Arguments

object	A longitudinal_grmtree object.
node	Optional vector of node IDs. If NULL, all terminal nodes.
clean_names	Logical. If TRUE (default), clean item names.
...	Additional arguments (currently unused).

Value

A data.frame with columns:

Node

Terminal node ID

Item

Item name

Discrimination

Discrimination parameter

AvgThreshold

Mean of all threshold parameters for the item

b1, b2, ..., bK

Individual threshold parameters

See Also

longitudinal_grmtree for Phase 1 (tree fitting), discrpar_longitudinal_grmtree for extracting discrimination parameters for longitudinal GRMTree, threshpar_longitudinal_grmtree for extracting threshold parameters for longitudinal GRMTree

Examples

library(grmtree)

# Load the synthetic longitudinal data
data("grmtree_long_data", package = "grmtree")

  # Prepare the wide-format response matrix
  items_t1 <- c("MOS_Listen", "MOS_Info", "MOS_Advice_Crisis", "MOS_Confide",
                "MOS_Advice_Want", "MOS_Fears", "MOS_Personal", "MOS_Understand")
  ld <- prepare_longitudinal_data(
    data = grmtree_long_data,
    items_t1 = items_t1,
    items_t2 = paste0(items_t1, "_year1"),
    covariates = c("sex", "age", "residency", "job",
                   "education", "comorbidity_count", "ever_smoker")
  )

  # Phase 1: fit the longitudinal GRM tree
  ltree <- longitudinal_grmtree(
    resp_wide ~ sex + age + residency + job +
      education + comorbidity_count + ever_smoker,
    data = ld, n_items = 8,
    control = grmtree.control(minbucket = 200)
  )

  # Print the item parameters
  items <- itempar_longitudinal_grmtree(ltree)
  print(items)

grmtree documentation built on Sept. 2, 2026, 1:07 a.m.