update deprecation of .as_matrix

doc/source/whatsnew/v0.22.0.txt

@@ -82,7 +82,7 @@ Deprecations
 ~~~~~~~~~~~~
 
 - ``Series.from_array`` and ``SparseSeries.from_array`` are deprecated. Use the normal constructor ``Series(..)`` and ``SparseSeries(..)`` instead (:issue:`18213`).
-- ``NDFrame.as_matrix`` is deprecated. Use ``NDFrame.values`` instead (:issue:`18458`).
+- ``DataFrame.as_matrix`` is deprecated. Use ``DataFrame.values`` instead (:issue:`18458`).
 -
 
 .. _whatsnew_0220.prior_deprecations:

pandas/core/generic.py

@@ -3736,7 +3736,7 @@ def _get_bool_data(self):
     def as_matrix(self, columns=None):
         """
         DEPRECATED: This method will be removed in a future version.
-        Use :meth:`NDFrame.values` instead.
+        Use :meth:`DataFrame.values` instead.
 
         Convert the frame to its Numpy-array representation.
 
@@ -3773,8 +3773,8 @@ def as_matrix(self, columns=None):
         --------
         pandas.DataFrame.values
         """
-        warnings.warn("This method will be removed in a future version. "
-                      "Use ``.values`` instead.")
+        warnings.warn(".as_matrix will be removed in a future version. "
+                      "Use .values instead.", FutureWarning, stacklevel=2)
         self._consolidate_inplace()
         if self._AXIS_REVERSED:
             return self._data.as_matrix(columns).T

pandas/tests/frame/test_api.py

@@ -369,6 +369,13 @@ def test_values(self):
         self.frame.values[:, 0] = 5.
         assert (self.frame.values[:, 0] == 5).all()
 
+    def test_as_matrix_deprecated(self):
+        # GH18458
+        with tm.assert_produces_warning(FutureWarning):
+            result = self.frame.as_matrix()
+        expected = self.frame.values
+        tm.assert_numpy_array_equal(result, expected)
+
     def test_deepcopy(self):
         cp = deepcopy(self.frame)
         series = cp['A']