fn group_rows_indices(
elt: SEXP,
group: usize,
nrow: usize,
) -> Result<Vec<usize>, DataFrameError>Expand description
Convert one .rows list element — an integer vector of 1-based row
indices (DataFrame::groups_attr checked its type) — into 0-based
indices, rejecting any index outside 1..=nrow (NA included).