Replace CubicSpline by make_interp_spline k=3

Author: jason-rpkt

pvlib/iam.py

@@ -470,7 +470,7 @@ def interp(aoi, theta_ref, iam_ref, method='linear', normalize=True):
     '''
     # Contributed by Anton Driesse (@adriesse), PV Performance Labs. July, 2019
 
-    from scipy.interpolate import CubicSpline, make_interp_spline
+    from scipy.interpolate import make_interp_spline
 
     # Scipy doesn't give the clearest feedback, so check number of points here.
     MIN_REF_VALS = {'linear': 2, 'quadratic': 3, 'cubic': 4, 1: 2, 2: 3, 3: 4}
@@ -499,7 +499,7 @@ def interpolator(x):
             return spline(x)
 
     elif method == "cubic":
-        spline = CubicSpline(theta_ref, iam_ref, extrapolate=True)
+        spline = make_interp_spline(theta_ref, iam_ref, k=3)
 
         def interpolator(x):
             return spline(x)

pvlib/spectrum/response.py

@@ -6,7 +6,7 @@
 import numpy as np
 import pandas as pd
 import scipy.constants
-from scipy.interpolate import CubicSpline
+from scipy.interpolate import make_interp_spline
 
 
 _PLANCK_BY_LIGHT_SPEED_OVER_ELEMENTAL_CHARGE_BY_BILLION = (
@@ -68,10 +68,9 @@ def get_example_spectral_response(wavelength=None):
         wavelength = np.arange(280, 1200 + resolution, resolution)
     x = SR_DATA[0]
     y = SR_DATA[1]
-    spline = CubicSpline(
-        x, y,
-        extrapolate=False
-    )
+    spline = make_interp_spline(
+        x, y, k=3)
+
     values = spline(wavelength)
     values[(wavelength < x[0]) | (wavelength > x[-1])] = 0.0