SEXP check_grouped(RObject data) {
static SEXP groups_symbol = Rf_install("groups");
static SEXP vars_symbol = Rf_install("vars");
// compat with old style grouped data frames
SEXP vars = Rf_getAttrib(data, vars_symbol);
if (!Rf_isNull(vars)) {
DataFrame groups = build_index_cpp(data, SymbolVector(vars));
data.attr("groups") = groups;
}
// get the groups attribute and check for consistency
SEXP groups = Rf_getAttrib(data, groups_symbol);
// groups must be a data frame
if (!is<DataFrame>(groups)) {
bad_arg(".data", "is a corrupt grouped_df, the `\"groups\"` attribute must be a data frame");
}
// it must have at least 1 column
int nc = Rf_length(groups);
if (nc <= 1) {
bad_arg(".data", "is a corrupt grouped_df, the `\"groups\"` attribute must have at least two columns");
}
// the last column must be a list and called `.rows`
SEXP names = Rf_getAttrib(groups, R_NamesSymbol);
SEXP last = VECTOR_ELT(groups, nc - 1);
static String rows = ".rows";
if (TYPEOF(last) != VECSXP || STRING_ELT(names, nc - 1) != rows) {
bad_arg(".data", "is a corrupt grouped_df, the `\"groups\"` attribute must have a list column named `.rows` as last column");
}
return data ;
}
SymbolVector GroupedDataFrame::group_vars(SEXP x) {
check_grouped(x);
static SEXP groups_symbol = Rf_install("groups");
SEXP groups = Rf_getAttrib(x, groups_symbol);
int n = Rf_length(groups) - 1;
CharacterVector vars = Rf_getAttrib(groups, R_NamesSymbol);
vars.erase(n);
return SymbolVector(vars);
}
SymbolVector get_vars(SEXP x) {
static SEXP vars_symbol = Rf_install("vars");
return SymbolVector(Rf_getAttrib(x, vars_symbol));
}
