deviation: Implement l1_dist

Author: munckymagik

src/deviation.rs

@@ -24,6 +24,10 @@ where
     fn l2_dist(&self, other: &ArrayBase<S, D>) -> f64
     where
         A: AddAssign + Clone + Signed + ToPrimitive;
+
+    fn l1_dist(&self, other: &ArrayBase<S, D>) -> A
+    where
+        A: AddAssign + Clone + Signed;
 }
 
 impl<A, S, D> DeviationExt<A, S, D> for ArrayBase<S, D>
@@ -74,6 +78,20 @@ where
     {
         self.sq_l2_dist(other).to_f64().unwrap().sqrt()
     }
+
+    fn l1_dist(&self, other: &ArrayBase<S, D>) -> A
+    where
+        A: AddAssign + Clone + Signed,
+    {
+        let mut r = A::zero();
+
+        Zip::from(self).and(other).apply(|self_i, other_i| {
+            let (a, b) = (self_i.clone(), other_i.clone());
+            r += (a - b).abs();
+        });
+
+        r
+    }
 }
 
 #[cfg(test)]
@@ -133,4 +151,15 @@ mod tests {
 
         assert_eq!(a.l2_dist(&b), 2.0);
     }
+
+    #[test]
+    fn test_l1_dist() {
+        let a = array![1., 2., 3., 4., 5., 6., 7.];
+        let b = array![1., 3., 3., 4., 6., 7., 8.];
+        let c = array![[1, 2], [3, 4], [5, 6]];
+        let d = array![[1, 2], [4, 3], [5, 6]];
+
+        assert_eq!(a.l1_dist(&b), (&a - &b).mapv(f64::abs).sum());
+        assert_eq!(c.l1_dist(&d), (&c - &d).mapv(i32::abs).sum());
+    }
 }