Deal with empty input arrays in kepler_spline.choose_kepler_spline().

PiperOrigin-RevId: 201007094

research/astronet/third_party/kepler_spline/kepler_spline.py

@@ -187,7 +187,8 @@ def choose_kepler_spline(all_time,
   # model and sigma is the constant standard deviation for all flux values.
   # Moreover, we assume that s[i] ~= s[i+1]. Therefore,
   # (f[i+1] - f[i]) / sqrt(2) ~ N(0, sigma^2).
-  scaled_diffs = np.concatenate([np.diff(f) / np.sqrt(2) for f in all_flux])
+  scaled_diffs = [np.diff(f) / np.sqrt(2) for f in all_flux]
+  scaled_diffs = np.concatenate(scaled_diffs) if scaled_diffs else np.array([])
   if not scaled_diffs.size:
     best_spline = [np.array([np.nan] * len(f)) for f in all_flux]
     metadata.light_curve_mask = [

research/astronet/third_party/kepler_spline/kepler_spline_test.py

@@ -79,6 +79,19 @@ class KeplerSplineTest(absltest.TestCase):
 
 class ChooseKeplerSplineTest(absltest.TestCase):
 
+  def testEmptyInput(self):
+    # Logarithmically sample candidate break point spacings.
+    bkspaces = np.logspace(np.log10(0.5), np.log10(5), num=20)
+
+    spline, metadata = kepler_spline.choose_kepler_spline(
+        all_time=[],
+        all_flux=[],
+        bkspaces=bkspaces,
+        penalty_coeff=1.0,
+        verbose=False)
+    np.testing.assert_array_equal(spline, [])
+    np.testing.assert_array_equal(metadata.light_curve_mask, [])
+
   def testNoPoints(self):
     all_time = [np.array([])]
     all_flux = [np.array([])]