GPIRT model-criticism interface — fit

`external` is the only exact GPIRT path. `spline_reference` fits flexible logistic spline IRFs solely as a nonparametric stress test for conventional logistic IRF shape; it is deliberately not described as a Gaussian process.

Usage

fit_gpirt(
  response_matrix,
  engine = c("spline_reference", "external"),
  external_engine = NULL,
  spline_df = 5L,
  ...
)

Arguments

response_matrix: Person-by-item response matrix.
engine: Estimation engine.
external_engine: Validated external fitting function.
spline_df: Degrees of freedom for the spline reference model.
...: Additional arguments passed to the selected model, engine, or method.