[Fix] UniformEncoder errors sorting alphanumerically with null values

rdt/transformers/ordinal.py

@@ -85,10 +85,10 @@ def _get_order(self, data):
                 order = order.sort_values(key=lambda x: x.astype(str))
 
             if pd.isna(data).any():
-                order = np.append(order, [np.nan])
+                order = pd.Series(np.append(order, [None]))
 
         if self.missing_value_encoding is None:
-            order = self.order[~pd.isna(self.order)]
+            order = self.order.dropna()
 
         return order
 

tests/integration/transformers/test_ordinal.py

@@ -14,6 +14,27 @@
 class TestOrderedUniformEncoder:
     """Test class for the OrderedUniformEncoder."""
 
+    def test_end_to_end(self):
+        """Test that transformer works end-to-end with default alphanumeric ordering."""
+        # Setup
+        data = pd.DataFrame({'column_name': [1.0, 2.0, 3.0, 2.0, np.nan, 1.0, 1.0, 0.0]})
+        transformer = OrderedUniformEncoder()
+        column = 'column_name'
+
+        # Run
+        with warnings.catch_warnings():
+            warnings.filterwarnings('error', module='rdt.transformers.categorical')
+            transformer.fit(data, column)
+            learned_order = transformer._get_order(data['column_name'])
+            transformed = transformer.transform(data)
+            reverse = transformer.reverse_transform(transformed)
+            expected_order = pd.Series([0, 1, 2, 3, None], dtype='object')
+
+        # Asserts
+        pd.testing.assert_series_equal(reverse[column], data[column])
+        pd.testing.assert_series_equal(learned_order, expected_order)
+        assert set(transformer.intervals.keys()) == {0, 1, 2, 3, None}
+
     def test_order(self):
         """Test that the ``order`` parameter is respected."""
         # Setup

tests/unit/transformers/test_ordinal.py

@@ -32,7 +32,7 @@ def test___init__(self):
         transformer = OrderedUniformEncoder(order=['b', 'c', 'a', None])
 
         # Asserts
-        pd.testing.assert_series_equal(transformer.order, pd.Series(['b', 'c', 'a', np.nan]))
+        pd.testing.assert_series_equal(transformer.order, pd.Series(['b', 'c', 'a', None]))
 
     def test___init___duplicate_categories(self):
         """Test the ``__init__`` method errors if duplicate categories provided.
@@ -108,7 +108,7 @@ def test__get_order_numerical(self):
         ordered = transformer._get_order(arr)
 
         # Assert
-        np.testing.assert_array_equal(ordered, np.array([-2.5, 3.11, 5, 67.8, 100, np.nan]))
+        np.testing.assert_array_equal(ordered, np.array([-2.5, 3.11, 5, 67.8, 100, None]))
 
     def test__order_warns_mixed_dtypes(self):
         """Test transformer warns if the data contains mixed dtypes."""