Added rounding of aa and b in _schumaker_qspline.py, see Issue #1311

pvlib · cwhanse · Nov 3, 2021 · Sep 27, 2021 · Oct 7, 2021 · Oct 7, 2021
commit 8136b5e40f2f2524581da2314a20bb4e1c75b622
diff --git a/pvlib/ivtools/utils.py b/pvlib/ivtools/utils.py
@@ -312,6 +312,11 @@ def _schumaker_qspline(x, y):

    aa = s[:-1] - delta
    b = s[1:] - delta
+
+    # Since the above two lines can lead to numerical errors, aa and b
+    # are rounded to 0.0 is their absolute value is small enough.
+    aa[np.isclose(aa, 0., atol=EPS)] = 0.
+    b[np.isclose(b, 0., atol=EPS)] = 0.

    sbar = np.zeros(k)
    eta = np.zeros(k)