Handle an empty list of persistence diagrams

2 files changed, 21 insertions, 0 deletions

diff --git a/src/python/gudhi/representations/vector_methods.py b/src/python/gudhi/representations/vector_methods.py
index 5133a64c..82f071d7 100644
--- a/src/python/gudhi/representations/vector_methods.py
+++ b/src/python/gudhi/representations/vector_methods.py
@@ -417,6 +417,9 @@ class BettiCurve2(BaseEstimator, TransformerMixin):
         """
 
         if self.predefined_grid is None:
+            if not X:
+                X = [np.zeros((0, 2))]
+            
             N = len(X)
 
             events = np.concatenate([pd.flatten(order="F") for pd in X], axis=0)
@@ -469,6 +472,9 @@ class BettiCurve2(BaseEstimator, TransformerMixin):
         if not self.is_fitted():
             raise NotFittedError("Not fitted.")
 
+        if not X:
+            X = [np.zeros((0, 2))]
+        
         N = len(X)
 
         events = np.concatenate([pd.flatten(order="F") for pd in X], axis=0)
diff --git a/src/python/test/test_betti_curve_representations.py b/src/python/test/test_betti_curve_representations.py
index 5b95fa2c..475839ee 100755
--- a/src/python/test/test_betti_curve_representations.py
+++ b/src/python/test/test_betti_curve_representations.py
@@ -37,3 +37,18 @@ def test_betti_curve_is_irregular_betti_curve_followed_by_interpolation():
         interp = scipy.interpolate.interp1d(bc.grid_, bettis[i, :], kind="previous", fill_value="extrapolate")
         bettis_interp = np.array(interp(grid), dtype=int)
         assert((bettis_interp == bettis_gridded).all())
+
+
+def test_empty_with_predefined_grid():
+    random_grid = np.sort(np.random.uniform(0, 1, 100))
+    bc = BettiCurve2(random_grid)
+    bettis = bc.fit_transform([])
+    assert((bc.grid_ == random_grid).all())
+    assert((bettis == 0).all())
+
+    
+def test_empty():
+    bc = BettiCurve2()
+    bettis = bc.fit_transform([])
+    assert(bc.grid_ == [-np.inf])
+    assert((bettis == 0).all())