BUG: pd.crosstab fails when passed multiple columns, margins True and normalize True (#35150)

Author: CloseChoice

doc/source/whatsnew/v1.2.0.rst

@@ -258,6 +258,7 @@ Reshaping
 
 - Bug in :meth:`DataFrame.pivot_table` with ``aggfunc='count'`` or ``aggfunc='sum'`` returning ``NaN`` for missing categories when pivoted on a ``Categorical``. Now returning ``0`` (:issue:`31422`)
 - Bug in :func:`union_indexes` where input index names are not preserved in some cases. Affects :func:`concat` and :class:`DataFrame` constructor (:issue:`13475`)
+- Bug in func :meth:`crosstab` when using multiple columns with ``margins=True`` and ``normalize=True`` (:issue:`35144`)
 -
 
 Sparse

pandas/core/reshape/pivot.py

@@ -670,12 +670,11 @@ def _normalize(table, normalize, margins: bool, margins_name="All"):
         # keep index and column of pivoted table
         table_index = table.index
         table_columns = table.columns
+        last_ind_or_col = table.iloc[-1, :].name
 
-        # check if margin name is in (for MI cases) or equal to last
+        # check if margin name is not in (for MI cases) and not equal to last
         # index/column and save the column and index margin
-        if (margins_name not in table.iloc[-1, :].name) | (
-            margins_name != table.iloc[:, -1].name
-        ):
+        if (margins_name not in last_ind_or_col) & (margins_name != last_ind_or_col):
             raise ValueError(f"{margins_name} not in pivoted DataFrame")
         column_margin = table.iloc[:-1, -1]
         index_margin = table.iloc[-1, :-1]

pandas/tests/reshape/test_crosstab.py

@@ -698,3 +698,48 @@ def test_margin_normalize(self):
             names=["A", "B"],
         )
         tm.assert_frame_equal(result, expected)
+
+    def test_margin_normalize_multiple_columns(self):
+        # GH 35144
+        # use multiple columns with margins and normalization
+        df = DataFrame(
+            {
+                "A": ["foo", "foo", "foo", "foo", "foo", "bar", "bar", "bar", "bar"],
+                "B": ["one", "one", "one", "two", "two", "one", "one", "two", "two"],
+                "C": [
+                    "small",
+                    "large",
+                    "large",
+                    "small",
+                    "small",
+                    "large",
+                    "small",
+                    "small",
+                    "large",
+                ],
+                "D": [1, 2, 2, 3, 3, 4, 5, 6, 7],
+                "E": [2, 4, 5, 5, 6, 6, 8, 9, 9],
+            }
+        )
+        result = crosstab(
+            index=df.C,
+            columns=[df.A, df.B],
+            margins=True,
+            margins_name="margin",
+            normalize=True,
+        )
+        expected = DataFrame(
+            [
+                [0.111111, 0.111111, 0.222222, 0.000000, 0.444444],
+                [0.111111, 0.111111, 0.111111, 0.222222, 0.555556],
+                [0.222222, 0.222222, 0.333333, 0.222222, 1.0],
+            ],
+            index=["large", "small", "margin"],
+        )
+        expected.columns = MultiIndex(
+            levels=[["bar", "foo", "margin"], ["", "one", "two"]],
+            codes=[[0, 0, 1, 1, 2], [1, 2, 1, 2, 0]],
+            names=["A", "B"],
+        )
+        expected.index.name = "C"
+        tm.assert_frame_equal(result, expected)