BUG: Closes #2015: diag returns ndarray

If x is a matrix, np.diag(x) and np.diagonal(x) now return matrices
instead of arrays.  Both of these cause x.diagonal() to be called.
That means they return row vectors (just like x.flatten(), x.ravel(),
x.cumprod(), etc.)

3 files changed, 13 insertions, 3 deletions

diff --git a/numpy/core/fromnumeric.py b/numpy/core/fromnumeric.py
index 84a10bf04..93ee07caa 100644
--- a/numpy/core/fromnumeric.py
+++ b/numpy/core/fromnumeric.py
@@ -1268,7 +1268,7 @@ def diagonal(a, offset=0, axis1=0, axis2=1):
            [5, 7]])
 
     """
-    return asarray(a).diagonal(offset, axis1, axis2)
+    return asanyarray(a).diagonal(offset, axis1, axis2)
 
 
 def trace(a, offset=0, axis1=0, axis2=1, dtype=None, out=None):
diff --git a/numpy/lib/twodim_base.py b/numpy/lib/twodim_base.py
index 40a140b6b..0c5065fa1 100644
--- a/numpy/lib/twodim_base.py
+++ b/numpy/lib/twodim_base.py
@@ -293,7 +293,7 @@ def diag(v, k=0):
            [0, 0, 8]])
 
     """
-    v = asarray(v)
+    v = asanyarray(v)
     s = v.shape
     if len(s) == 1:
         n = s[0]+abs(k)
diff --git a/numpy/matrixlib/tests/test_numeric.py b/numpy/matrixlib/tests/test_numeric.py
index 3588de5e6..91dc92d2e 100644
--- a/numpy/matrixlib/tests/test_numeric.py
+++ b/numpy/matrixlib/tests/test_numeric.py
@@ -2,12 +2,22 @@ from __future__ import division, absolute_import, print_function
 
 from numpy.testing import assert_equal, TestCase, run_module_suite
 from numpy.core import ones
-from numpy import matrix
+from numpy import matrix, diagonal, diag
 
 class TestDot(TestCase):
     def test_matscalar(self):
         b1 = matrix(ones((3, 3), dtype=complex))
         assert_equal(b1*1.0, b1)
 
+
+def test_diagonal():
+    b1 = matrix([[1,2],[3,4]])
+    diag_b1 = matrix([[1, 4]])
+
+    assert_equal(b1.diagonal(), diag_b1)
+    assert_equal(diagonal(b1), diag_b1)
+    assert_equal(diag(b1), diag_b1)
+
+
 if __name__ == "__main__":
     run_module_suite()