Add wsinterp test for coverage

Author: Sparks29032

src/diffpy/utils/parsers/resample.py

@@ -43,8 +43,10 @@ def wsinterp(x, xp, fp, left=None, right=None):
 
     Returns
     -------
+    float:
+        If input x is a scalar (not an array), return the interpolated value at x.
     ndarray:
-        Returns the interpolated array with dimensions of x.
+        If input x is an array, return the interpolated array with dimensions of x.
     """
     scalar = numpy.isscalar(x)
     if scalar:
@@ -58,12 +60,14 @@ def wsinterp(x, xp, fp, left=None, right=None):
     # shape = (nx, nxp), m(v) data spans axis 1
     m = fp * numpy.sinc(v)
     # Sum over m(v) (axis 1)
-    fp_at_x = numpy.sum(m, axis = 1)
+    fp_at_x = numpy.sum(m, axis=1)
 
     # Enforce left and right
-    if left is None: left = fp[0]
+    if left is None:
+        left = fp[0]
     fp_at_x[x < xp[0]] = left
-    if right is None: right = fp[-1]
+    if right is None:
+        right = fp[-1]
     fp_at_x[x > xp[-1]] = right
 
     # Return a float if we got a float

src/diffpy/utils/tests/test_resample.py

@@ -0,0 +1,30 @@
+import pytest
+import numpy as np
+
+from diffpy.utils.parsers.resample import wsinterp
+
+
+def test_wsinterp():
+    import random
+    # Check known points are unchanged by interpolation
+    # FIXME: if another SW interp function exists, run comparisons for interpolated points
+
+    # Sampling rate
+    ssr = 44100**-1  # Standard sampling rate for human-hearable frequencies
+    t = ssr
+    n = 5  # Do 6 samples
+    xp = np.array([i*t for i in range(-n, n+1, 1)])
+    x = np.array([i*t for i in range(-n-1, n+2, 1)])
+
+    # Interpolate a few random datasets
+    trials = 10
+    for trial in range(trials):
+        fp = np.array([random.random() * ssr for i in range(-n, n+1, 1)])
+        fp_at_x = wsinterp(x, xp, fp)
+        assert np.allclose(fp_at_x[1:-1], fp)
+        for i in range(len(x)):
+            assert fp_at_x[i] == pytest.approx(wsinterp(x[i], xp, fp))
+
+
+if __name__ == '__main__':
+    test_wsinterp()