Check collinearity using VIF for fitted models — check

Computes Variance Inflation Factors (VIF) for fitted multivariable models returned by multi_reg() or related functions.

Usage

check_collinearity(model, format = c("flextable", "gt", "tibble"))

Arguments

model: A fitted model object returned by multi_reg(), stratified_multi_reg(), or compatible gtregression functions. Univariable model objects are rejected because VIF is not applicable.
format: Output format. One of "flextable" (default), "gt", or "tibble". Use format = "tibble" to preserve the original tibble or nested-list output.

Value

For multivariable models, a tibble if a single fitted model is present, or a named list of tibbles if multiple fitted models are present. With format = "gt" or format = "flextable", leaf tibbles are converted to formatted tables while preserving any list nesting. The tibble contains:

Variable: Model term.
VIF: Variance inflation factor. For multi-degree-of-freedom terms, this is the adjusted GVIF: GVIF^(1 / (2 * Df)).
Interpretation: Simple interpretation based on common cut points: no collinearity, moderate, or high.

For univariate models, an error is raised indicating that VIF is not applicable.

Details

If the car package is installed, check_collinearity() uses car::vif(). Otherwise, it computes VIF/GVIF from the fitted model matrix so that diagnostics remain available without an additional dependency.