News for Package crrstep

Changes in version 2025.1.0

• Major rewrite to properly handle complex formula terms including:

  • Factor variables with multiple levels

  • Interaction terms (e.g., x1:x2, x1:factor)

  • Polynomial terms (e.g., I(x^2))

  • Complex interactions with polynomials (e.g., I(x^2):factor)

  • Log transformations with interactions (e.g., log(x):factor)

  • Three-way and higher-order interactions

• Fixed bug where null model returned incorrect log-likelihood. Previously, when the null model was selected, the function returned the log-likelihood of the last non-null model instead of the actual null model log-likelihood (loglik.null).

• Eliminated deprecation warning related to formula.character() for formulas with length > 1.

• Improved term handling using the assign attribute from model.matrix() to correctly identify which columns belong to which terms.

• Added helper functions for safer formula manipulation:

  • safe_as_formula(): Safely converts various inputs to formula objects

  • safe_drop_term(): Drops terms by reconstructing formula from term labels

  • safe_add_term(): Adds terms by reconstructing formula string

• Replaced regex-based column matching with proper assign attribute tracking, fixing issues where variable names contained other variable names as substrings.

• Added explicit namespace prefixes (stats::, cmprsk::) for CRAN compliance.

Changes in version 2015-2.1

• Corrected a bug in backward selection procedure in how scope.min was checked to terminate the selection procedure.

• Added checks to make sure that scope.min formula input is correct.

• Simplified how standard error was computed.

• Fixed a bug related to outputting results in forward selection.

Changes in version 2014-07.16

• Corrected a bug in backward selection procedure when one variable name is contained in another variable name (e.g., "Mitosis" and "AtyMitosis").

• Corrected a bug in forward selection procedure when an as.factor() variable is to be added to the model.