FIX MaxAbsScaler on sparse matrices with 1 row

Jeffrey04 · ogrisel · commit 00996a23a628 · 2015-10-21T12:11:15.000+02:00
diff --git a/sklearn/preprocessing/data.py b/sklearn/preprocessing/data.py
@@ -788,10 +788,7 @@ def transform(self, X, y=None):
             warnings.warn(DEPRECATION_MSG_1D, DeprecationWarning)
 
         if sparse.issparse(X):
-            if X.shape[0] == 1:
-                inplace_row_scale(X, 1.0 / self.scale_)
-            else:
-                inplace_column_scale(X, 1.0 / self.scale_)
+            inplace_column_scale(X, 1.0 / self.scale_)
         else:
             X /= self.scale_
         return X
@@ -811,10 +808,7 @@ def inverse_transform(self, X):
             warnings.warn(DEPRECATION_MSG_1D, DeprecationWarning)
 
         if sparse.issparse(X):
-            if X.shape[0] == 1:
-                inplace_row_scale(X, self.scale_)
-            else:
-                inplace_column_scale(X, self.scale_)
+            inplace_column_scale(X, self.scale_)
         else:
             X *= self.scale_
         return X
diff --git a/sklearn/preprocessing/tests/test_data.py b/sklearn/preprocessing/tests/test_data.py
@@ -937,6 +937,18 @@ def test_maxabs_scaler_large_negative_value():
     assert_array_almost_equal(X_trans, X_expected)
 
 
+def test_maxabs_scaler_transform_one_row_csr():
+    """Check MaxAbsScaler on transforming csr matrix with one row"""
+    X = sparse.csr_matrix([[0.5, 1., 1.]])
+    scaler = MaxAbsScaler()
+    scaler = scaler.fit(X)
+    X_trans = scaler.transform(X)
+    X_expected = sparse.csr_matrix([[1., 1., 1.]])
+    assert_array_almost_equal(X_trans.toarray(), X_expected.toarray())
+    X_scaled_back = scaler.inverse_transform(X_trans)
+    assert_array_almost_equal(X.toarray(), X_scaled_back.toarray())
+
+
 @ignore_warnings
 def test_deprecation_minmax_scaler():
     rng = np.random.RandomState(0)
