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fix: ml.model_selection.train_test_split index to match in unordered mode #2283

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fix: ml.model_selection.train_test_split index to match in unordered mode #2283

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fix: ml.model_selection.train_test_split index to match in unordered …
GarrettWu Nov 19, 2025
9e2cd71
fix
GarrettWu Nov 20, 2025
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5 changes: 3 additions & 2 deletions bigframes/ml/model_selection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,7 @@ def _stratify_split(df: bpd.DataFrame, stratify: bpd.Series) -> List[bpd.DataFra
joined_df = dfs[0]
for df in dfs[1:]:
joined_df = joined_df.join(df, how="outer")
joined_df = joined_df.cache()
if stratify is None:
joined_df_train, joined_df_test = joined_df._split(
fracs=(train_size, test_size), random_state=random_state
Expand All @@ -120,8 +121,8 @@ def _stratify_split(df: bpd.DataFrame, stratify: bpd.Series) -> List[bpd.DataFra
results = []
for array in arrays:
columns = array.name if isinstance(array, bpd.Series) else array.columns
results.append(joined_df_train[columns])
results.append(joined_df_test[columns])
results.append(joined_df_train[columns].cache())
results.append(joined_df_test[columns].cache())

return results

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18 changes: 18 additions & 0 deletions tests/system/small/ml/test_model_selection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,24 @@ def test_train_test_split_default_correct_shape(df_fixture, request):
assert y_test.shape == (86, 1)


def test_train_test_split_default_unordered_same_index(
unordered_session, penguins_pandas_df_default_index
):
df = unordered_session.read_pandas(penguins_pandas_df_default_index)
X = df[
[
"species",
"island",
"culmen_length_mm",
]
]
y = df[["body_mass_g"]]
X_train, X_test, y_train, y_test = model_selection.train_test_split(X, y)

pd.testing.assert_index_equal(X_train.to_pandas().index, y_train.to_pandas().index)
pd.testing.assert_index_equal(X_test.to_pandas().index, y_test.to_pandas().index)


def test_train_test_split_series_default_correct_shape(penguins_df_default_index):
X = penguins_df_default_index[["species"]]
y = penguins_df_default_index["body_mass_g"]
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