Compare fitted mixeff models — compare • mixeff

compare() is the namespace-qualified model-comparison front door. For LMMs it reports likelihood, information criteria, and asymptotic likelihood-ratio comparisons. REML fits are refit by ML when refit_for_comparison = "auto" or "ml"; "error" refuses that comparison.

Usage

compare(object, ...)

# S3 method for class 'mm_lmm'
compare(
  object,
  ...,
  target = c("fixed_effects", "random_effects", "prediction"),
  method = c("auto", "lrt", "bootstrap", "aic", "kenward_roger", "satterthwaite"),
  refit_for_comparison = c("auto", "error", "ml"),
  nsim = 0L,
  seed = NULL,
  threads = 1L
)

Arguments

object: A fitted mm_lmm.
...: Additional fitted mm_lmm objects.
target: Comparison target label.
method: "auto" / "lrt" for asymptotic likelihood-ratio rows, "aic" for information criteria only, "bootstrap" for a small parametric-bootstrap LRT when nsim > 0, or "kenward_roger" / "satterthwaite" for pbkrtest's KRmodcomp() / SATmodcomp(): an F test of the larger model's fixed effects restricted to the smaller model's (two models with identical random effects, nested in their fixed effects). The restriction matrix is built from the two design matrices as pbkrtest does; the test runs on the REML fit of the larger model (refitted by REML if it was fitted by ML, as pbkrtest does). The Kenward-Roger F is pbkrtest's scaled statistic (the main Ftest row of KRmodcomp(), which lmerTest's anova(ddf = "Kenward-Roger") also reports): $F = \lambda F_U$ referred to $F(q, \nu)$ with the KR denominator df, where $\lambda$ is the KR scaling factor (f_scaling; 1 for a single restriction). The unscaled statistic and its p-value (pbkrtest's FtestU row) are kept as unscaled_statistic / unscaled_p_value. The F row replaces the LRT row (statistic_name = "F", df = numerator df, den_df = denominator df); the full result is in $fixed_f.
refit_for_comparison: How to handle REML fits.
nsim: Number of bootstrap simulations for method = "bootstrap".
seed: Optional bootstrap seed.
threads: Worker threads for the bootstrap refits (default 1; see bootstrap_control()). The result is identical for every value.

Value

An mm_model_comparison object with a data-frame table.