// [[Rcpp::export]]
S4 CPP_scale_margins_sparse(S4 M, NumericVector rows, NumericVector cols, bool duplicate = true) {
if (!M.is("dgCMatrix"))
stop("internal error -- not a canonical sparse matrix");
IntegerVector dims = M.slot("Dim");
int nr = dims[0], nc = dims[1];
if (nr != rows.size() || nc != cols.size())
stop("internal error -- row/column weights not conformable with matrix");
if (duplicate)
M = clone(M);
IntegerVector p = M.slot("p");
IntegerVector::iterator _p = p.begin();
IntegerVector row_of = M.slot("i");
IntegerVector::iterator _row_of = row_of.begin();
NumericVector x = M.slot("x");
NumericVector::iterator _x = x.begin();
NumericVector::iterator _rows = rows.begin();
for (int col = 0; col < nc; col++) {
double col_weight = cols[col];
for (int i = _p[col]; i < _p[col+1]; i++) {
_x[i] *= _rows[_row_of[i]] * col_weight;
}
}
return M;
}
