add tests for periodic

tests/cubic_spline_strat.rs

@@ -416,7 +416,7 @@ fn bounds_shape_error1() {
     let y = array![[0.5, 1.0], [0.0, 1.5], [3.0, 0.5],];
     let boundaries = BoundaryCondition::Individual(array![[
         RowBoundary::Natural,
-        RowBoundary::Periodic,
+        RowBoundary::Clamped,
         RowBoundary::NotAKnot
     ],]);
     Interp1DBuilder::new(y)
@@ -440,23 +440,63 @@ fn bounds_shape_error2() {
 }
 
 #[test]
-#[should_panic(expected = "First: 1.0, last: 0.5")]
+#[should_panic(
+    expected = "First: [0.5, 1.0], shape=[2], strides=[1], layout=CFcf (0xf), const ndim=1, last: [0.5, 1.1]"
+)]
 fn periodic_wrong_values() {
-    let y = array![[0.5, 1.0], [0.0, 1.5], [3.0, 0.5],];
-    let boundaries =
-        BoundaryCondition::Individual(array![[RowBoundary::Natural, RowBoundary::Periodic],]);
+    let y = array![[0.5, 1.0], [0.0, 1.5], [0.5, 1.1],];
     Interp1DBuilder::new(y)
-        .strategy(CubicSpline::new().boundary(boundaries))
+        .strategy(CubicSpline::new().boundary(BoundaryCondition::Periodic))
         .build()
         .unwrap();
 }
 
 #[test]
-#[should_panic(expected = "First: [0.5, 1.0], shape=[2], strides=[1], layout=CFcf (0xf), const ndim=1, last: [0.5, 1.1]")]
-fn periodic_wrong_values2() {
-    let y = array![[0.5, 1.0], [0.0, 1.5], [0.5, 1.1],];
-    Interp1DBuilder::new(y)
-        .strategy(CubicSpline::new().boundary(BoundaryCondition::Periodic))
+fn extrapolate_periodic() {
+    let data = array![1.0, 2.0, 2.5, 2.5, 3.0, 2.0, 1.0, -2.0, 3.0, 5.0, 6.3, 1.0];
+    let interp = Interp1D::builder(data)
+        .strategy(
+            CubicSpline::new()
+                .extrapolate(true)
+                .boundary(BoundaryCondition::Periodic),
+        )
         .build()
         .unwrap();
+    let q = Array1::linspace(-3.0, 15.0, 30);
+    let res = interp.interp_array(&q).unwrap();
+
+    // values from scipy.interpolate.QubicSpline with bc_type=((1,-0.1),(1,-0.5))
+    let expect = array![
+        3.,
+        4.45171164,
+        5.5978812,
+        6.54905092,
+        3.79486808,
+        0.76011398,
+        1.36656494,
+        2.4432986,
+        2.50822019,
+        2.40158688,
+        2.63514361,
+        3.01451693,
+        2.59950279,
+        1.96267846,
+        1.65029582,
+        -0.22831889,
+        -2.04318459,
+        0.41031552,
+        3.63201944,
+        4.66215778,
+        6.05245899,
+        6.19632834,
+        2.68818585,
+        0.64246067,
+        1.77979077,
+        2.52789822,
+        2.46676892,
+        2.41681682,
+        2.76866398,
+        3.
+    ];
+    assert_relative_eq!(res, expect, epsilon = f64::EPSILON, max_relative = 0.001);
 }