FIX expit bug with out != None

Author: larsmans

sklearn/utils/fixes.py

@@ -38,7 +38,8 @@ def expit(x, out=None):
         See sklearn.utils.extmath.log_logistic for the log of this function.
         """
         if out is None:
-            out = np.copy(x)
+            out = np.empty(np.atleast_1d(x).shape, dtype=np.float64)
+        out[:] = x
 
         # 1 / (1 + exp(-x)) = (1 + tanh(x / 2)) / 2
         # This way of computing the logistic is both fast and stable.
@@ -47,7 +48,7 @@ def expit(x, out=None):
         out += 1
         out *= .5
 
-        return out
+        return out.reshape(np.shape(x))
 
 
 # little danse to see if np.copy has an 'order' keyword argument

sklearn/utils/tests/test_fixes.py

@@ -6,7 +6,9 @@
 import numpy as np
 
 from nose.tools import assert_equal
-from numpy.testing import assert_almost_equal, assert_array_equal
+from numpy.testing import (assert_almost_equal,
+                           assert_array_almost_equal,
+                           assert_array_equal)
 
 from ..fixes import divide, expit
 
@@ -20,6 +22,10 @@ def test_expit():
     assert_almost_equal(expit(-1000.), np.exp(-1000.) / (1. + np.exp(-1000.)),
                         decimal=16)
 
+    x = np.arange(10)
+    out = np.zeros_like(x, dtype=np.float32)
+    assert_array_almost_equal(expit(x), expit(x, out=out))
+
 
 def test_divide():
     assert_equal(divide(.6, 1), .600000000000)