pub fn contingency_table_from_indices<S1: BuildHasher, S2: BuildHasher>(
indices: &[usize],
x_values: &Array1<f64>,
y_values: &Array1<f64>,
x_categories: &HashMap<OrderedFloat<f64>, usize, S1>,
y_categories: &HashMap<OrderedFloat<f64>, usize, S2>,
) -> Array2<f64>