Workaround for axis_windows bug

rust-ndarray/ndarray#1304

Author: jonasBoss

src/interp1d/strategies/cubic_spline.rs

@@ -4,8 +4,7 @@ use std::{
 };
 
 use ndarray::{
-    s, Array, ArrayBase, ArrayViewMut, Axis, Data, Dimension, Ix1, RemoveAxis, ScalarOperand,
-    Slice, Zip,
+    s, Array, ArrayBase, ArrayViewMut, Axis, Data, Dimension, Ix1, RemoveAxis, ScalarOperand, Zip,
 };
 use num_traits::{cast, Num, NumCast, Pow};
 
@@ -132,27 +131,23 @@ impl CubicSpline {
         // RHS vector
         let mut rhs: Array<Sd::Elem, D> = Array::zeros(dim.clone());
 
-        let mut inner_rhs = rhs.slice_axis_mut(AX0, Slice::from(1..-1));
-        Zip::from(inner_rhs.axis_iter_mut(AX0))
-            .and(x.windows(3))
-            .and(data.axis_windows(AX0, 3))
-            .for_each(|rhs, x, data| {
-                let y_left = data.index_axis(AX0, 0);
-                let y_mid = data.index_axis(AX0, 1);
-                let y_right = data.index_axis(AX0, 2);
-                let x_left = x[0];
-                let x_mid = x[1];
-                let x_right = x[2];
-
-                Zip::from(y_left).and(y_mid).and(y_right).map_assign_into(
-                    rhs,
-                    |&y_left, &y_mid, &y_right| {
-                        three
-                            * ((y_mid - y_left) / (x_mid - x_left).pow(two)
-                                + (y_right - y_mid) / (x_right - x_mid).pow(two))
-                    },
-                );
-            });
+        for i in 1..len-1{
+            let rhs = rhs.index_axis_mut(AX0, i);
+            let y_left = data.index_axis(AX0, i-1);
+            let y_mid = data.index_axis(AX0, i);
+            let y_right = data.index_axis(AX0, i+1);
+            let x_left = x[i-1];
+            let x_mid = x[i];
+            let x_right = x[i+1];
+            Zip::from(y_left).and(y_mid).and(y_right).map_assign_into(
+                rhs,
+                |&y_left, &y_mid, &y_right| {
+                    three
+                        * ((y_mid - y_left) / (x_mid - x_left).pow(two)
+                            + (y_right - y_mid) / (x_right - x_mid).pow(two))
+                },
+            );
+        }
 
         let rhs_0 = rhs.index_axis_mut(AX0, 0);
         let data_0 = data.index_axis(AX0, 0);