Add citation to wsint, remove empty line, add 'the' in docstrings

Author: bobleesj

src/diffpy/utils/resampler.py

@@ -24,6 +24,7 @@ def wsinterp(x, xp, fp, left=None, right=None):
     Reconstruct a continuous signal from discrete data points by utilizing sinc functions
     as interpolation kernels. This function interpolates the values of fp (array),
     which are defined over xp (array), at new points x (array or float).
+    The implementation is based on E. T. Whittaker's 1915 paper (https://doi.org/10.1017/S0370164600017806).
 
     Parameters
     ----------
@@ -32,7 +33,7 @@ def wsinterp(x, xp, fp, left=None, right=None):
     xp: ndarray
         The array of known x values.
     fp: ndarray
-        The array of y values associated xp.
+        The array of y values associated with xp.
     left: float
         If given, set fp for x < xp[0] to left. Otherwise, if left is None (default) or not given,
         set fp for x < xp[0] to fp evaluated at xp[-1].
@@ -43,7 +44,7 @@ def wsinterp(x, xp, fp, left=None, right=None):
     Returns
     -------
     ndarray or float
-        Interpolated values at points x. Returns a single float if x is a scalar,
+        The interpolated values at points x. Returns a single float if x is a scalar,
         otherwise returns a numpy.ndarray.
     """
     scalar = np.isscalar(x)

tests/test_resample.py

@@ -18,21 +18,15 @@ def test_wsinterp():
     x = np.array([i * ssr for i in range(-n - 1, n + 2, 1)])
     assert len(xp) == 11 and len(x) == 13
 
-    # Generating fp values across 10 trial runs
+    # Generating a new set of fp values across 10 trial runs
     trials = 10
 
     for _ in range(trials):
         # Create random function values (fp) at the points defined in xp above
         fp = np.array([random.random() * ssr for _ in range(-n, n + 1, 1)])
-
-        # Interpolate the values at new x points
         fp_at_x = wsinterp(x, xp, fp)
 
         # Check that the known points are unchanged by interpolation
         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()