fix needless-range and clippy::ptr_arg warnings. (#36)

* Fix needless for loop range

* Do not ignore clippy::ptr_arg

src/metrics/cluster_helpers.rs

@@ -1,3 +1,4 @@
+#![allow(clippy::ptr_arg)]
 use std::collections::HashMap;
 
 use crate::math::num::RealNumber;
@@ -23,7 +24,7 @@ pub fn contingency_matrix<T: RealNumber>(
     contingency_matrix
 }
 
-pub fn entropy<T: RealNumber>(data: &Vec<T>) -> Option<T> {
+pub fn entropy<T: RealNumber>(data: &[T]) -> Option<T> {
     let mut bincounts = HashMap::with_capacity(data.len());
 
     for e in data.iter() {
@@ -44,17 +45,17 @@ pub fn entropy<T: RealNumber>(data: &Vec<T>) -> Option<T> {
     Some(entropy)
 }
 
-pub fn mutual_info_score<T: RealNumber>(contingency: &Vec<Vec<usize>>) -> T {
+pub fn mutual_info_score<T: RealNumber>(contingency: &[Vec<usize>]) -> T {
     let mut contingency_sum = 0;
     let mut pi = vec![0; contingency.len()];
     let mut pj = vec![0; contingency[0].len()];
     let (mut nzx, mut nzy, mut nz_val) = (Vec::new(), Vec::new(), Vec::new());
 
     for r in 0..contingency.len() {
-        for c in 0..contingency[0].len() {
+        for (c, pj_c) in pj.iter_mut().enumerate().take(contingency[0].len()) {
             contingency_sum += contingency[r][c];
             pi[r] += contingency[r][c];
-            pj[c] += contingency[r][c];
+            *pj_c += contingency[r][c];
             if contingency[r][c] > 0 {
                 nzx.push(r);
                 nzy.push(c);