Function pre_eval_subset 

fn pre_eval_subset(
    args: &[Arg],
    env: &Environment,
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Subset a data frame by condition and/or column selection.

Evaluates the subset expression in the context of the data frame’s columns, keeping rows where it evaluates to TRUE. The select argument specifies which columns to keep.

@param x a data frame @param subset logical expression evaluated in the data frame context @param select expression indicating columns to select (e.g., c(a, b) or -c) @return subsetted data frame