Import an eRm fit to an mfrmr-compatible bundle

Extracts item / person parameters from an eRm::PCM(), eRm::RM() or eRm::RSM() fit. Source cumulative easiness coefficients are converted to absolute adjacent-category difficulties. One item location is returned per item: the mean of its thresholds. Source identification is retained. Current eRm person tables use Person Parameter and Std.Error; historical theta / thetapar estimate labels are also accepted. Unknown or internally misaligned person-table schemas stop with an explicit error rather than silently recycling rows. Same caveats as import_mirt_fit().

Usage

import_erm_fit(fit, model = c("RSM", "PCM", "GPCM"), item_facet = "Item")

Arguments

fit: An object returned by eRm::PCM(), eRm::RM(), or eRm::RSM().
model: Matching "PCM" or "RSM" label; either is accepted for a binary RM. "GPCM" and linear extensions are unsupported.
item_facet: Name to assign to the item facet.

Value

An mfrm_imported_fit object.

Details

Item-location SEs use the corresponding scalar transformation of the source cumulative coefficient SE. Person maximum-likelihood estimates and conditional SEs retain source conventions, including labelled extreme-score extrapolations. The original coefficient table is retained in source$native_parameters.

Imported uncertainty

Imported SEs retain the source package's interpretation. The measurement-side diagnostics do not reconstruct the joint parameter covariance, so joint facet chi-square statistics, degrees of freedom and p-values are unavailable. Posterior SDs do not supply sampling SEs for separation reliability. Other separation summaries require valid SEs for every finite estimate and remain descriptive. Imported Wright maps show points only: source uncertainty conventions do not establish one common confidence-interval calculation. Re-import older saved bundles from the existing source-package fit to update difficulties, thresholds and uncertainty labels. The mirt and TAM importers accept compute_fit = TRUE when source fit statistics are needed; no model re-estimation is required.

Scope

Use summary() for source-scale tables and plot() for a point-only Wright map. Available source fit statistics remain in the facet and diagnostic tables. Native model curves, comprehensive mfrm_results() reports, response-level diagnostics, run_qc_pipeline(), bias/DIF analysis, anchoring and portable calibration are unavailable for imported bundles. This is a one-way fitted-object import of the documented fields.

Examples

# \donttest{
if (requireNamespace("eRm", quietly = TRUE)) {
  response_matrix <- matrix(sample(0:3, 60, replace = TRUE), nrow = 20)
  colnames(response_matrix) <- paste0("Item", seq_len(ncol(response_matrix)))
  fit <- eRm::PCM(response_matrix)
  imported <- import_erm_fit(fit, model = "PCM")
  imported$summary
}
#>   Model Method Source  N Persons Facets Categories    LogLik AIC BIC Converged
#> 1   PCM    CML    eRm 20      20      1         NA -38.17201  NA  NA      TRUE
#>   ConvergenceStatus
#> 1          imported
# }

Import an `eRm` fit to an mfrmr-compatible bundle