Remove extrapolation from resample_spline

Closes #146

src/ramanchada2/spectrum/filters/resampling.py

@@ -150,6 +150,7 @@ def resample_spline(spe: Spectrum, /,
     kw_args: Dict[str, Any] = {}
     if spline == 'pchip':
         spline_fn = PchipInterpolator
+        kw_args['extrapolate'] = False
     elif spline == 'akima':
         spline_fn = Akima1DInterpolator
     elif spline == 'makima':
@@ -158,6 +159,7 @@ def resample_spline(spe: Spectrum, /,
     elif spline == 'cubic_spline':
         spline_fn = CubicSpline
         kw_args['bc_type'] = 'natural'
+        kw_args['extrapolate'] = False
 
     if interp_kw_args is not None:
         kw_args.update(interp_kw_args)

tests/spectrum/filters/test_resample_spline.py

@@ -1,7 +1,8 @@
-import ramanchada2 as rc2
 import numpy as np
 from scipy.interpolate import CubicSpline
 
+import ramanchada2 as rc2
+
 
 def test_resample_spline():
     spe = rc2.spectrum.from_test_spe(2, laser_wl=['785'], sample=['PST']).normalize()
@@ -10,3 +11,11 @@ def test_resample_spline():
     aaa = CubicSpline(spe_tr.x, spe_tr.y)(np.linspace(400, 2000, 1000, endpoint=False))
     assert np.all(res_spe.x == np.linspace(400, 2000, 1000, endpoint=False))
     assert np.allclose(aaa, res_spe.y, rtol=.05)
+
+    spe = rc2.spectrum.from_delta_lines({500: 100, 600: 200})
+    spe = spe.add_gaussian_noise_drift(sigma=2, coef=.3)
+
+    for s in 'pchip', 'akima', 'makima', 'cubic_spline':
+        tt = spe.resample_spline_filter(x_range=(0, 1000), xnew_bins=1000, spline=s)
+        assert np.all(tt.y[:450] == 0)
+        assert np.all(tt.y[650:] == 0)