deviation: Implement root_mean_sq_dev (no normalize param)

Author: munckymagik

src/deviation.rs

@@ -48,6 +48,10 @@ where
     fn mean_sq_dev(&self, other: &ArrayBase<S, D>) -> A
     where
         A: AddAssign + Clone + FromPrimitive + Signed;
+
+    fn root_mean_sq_dev(&self, other: &ArrayBase<S, D>) -> A
+    where
+        A: AddAssign + Clone + FromPrimitive + Signed + Float;
 }
 
 impl<A, S, D> DeviationExt<A, S, D> for ArrayBase<S, D>
@@ -165,15 +169,24 @@ where
     {
         self.sq_l2_dist(other) / A::from_usize(self.len()).unwrap()
     }
+
+    fn root_mean_sq_dev(&self, other: &ArrayBase<S, D>) -> A
+    where
+        A: AddAssign + Clone + FromPrimitive + Signed + Float
+    {
+        self.mean_sq_dev(other).sqrt()
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use approx::assert_abs_diff_eq;
     use ndarray::*;
     use ndarray_rand::RandomExt;
     use num_traits::Pow;
     use rand::distributions::Uniform;
+    use std::f64;
 
     #[test]
     fn test_count_eq() {
@@ -304,4 +317,14 @@ mod tests {
         assert_eq!(a.mean_sq_dev(&b), 10.);
         assert_eq!(b.mean_sq_dev(&a), 10.);
     }
+
+    #[test]
+    fn test_root_mean_sq_dev() {
+        let a = array![1., 1.];
+        let b = array![3., 5.];
+
+        assert_eq!(a.root_mean_sq_dev(&a), 0.);
+        assert_abs_diff_eq!(a.root_mean_sq_dev(&b), 10.0.sqrt(), epsilon = f64::EPSILON);
+        assert_abs_diff_eq!(b.root_mean_sq_dev(&a), 10.0.sqrt(), epsilon = f64::EPSILON);
+    }
 }