BUG: np.ma.compress treated inputs in wrong order; closes #2495

2 files changed, 21 insertions, 2 deletions

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index 223f119b8..99b3e4efc 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -5975,9 +5975,10 @@ class _frommethod:
         Name of the method to transform.
 
     """
-    def __init__(self, methodname):
+    def __init__(self, methodname, reversed=False):
         self.__name__ = methodname
         self.__doc__ = self.getdoc()
+        self.reversed = reversed
     #
     def getdoc(self):
         "Return the doc of the function (from the doc of the method)."
@@ -5989,6 +5990,11 @@ class _frommethod:
             return doc
     #
     def __call__(self, a, *args, **params):
+        if self.reversed:
+            args = list(args)
+            arr = args[0]
+            args[0] = a
+            a = arr
         # Get the method from the array (if possible)
         method_name = self.__name__
         method = getattr(a, method_name, None)
@@ -6005,7 +6011,7 @@ class _frommethod:
 all = _frommethod('all')
 anomalies = anom = _frommethod('anom')
 any = _frommethod('any')
-compress = _frommethod('compress')
+compress = _frommethod('compress', reversed=True)
 cumprod = _frommethod('cumprod')
 cumsum = _frommethod('cumsum')
 copy = _frommethod('copy')
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
index 263a9735a..393513eba 100644
--- a/numpy/ma/tests/test_core.py
+++ b/numpy/ma/tests/test_core.py
@@ -3381,6 +3381,19 @@ class TestMaskedArrayFunctions(TestCase):
         test = reshape(a, (2, 2))
         assert_equal(test, m.reshape(2, 2))
 
+    def test_compress(self):
+        # Test compress function on ndarray and masked array
+        # Address Github #2495.
+        arr = np.arange(8)
+        arr.shape = 4,2
+        cond = np.array([True, False, True, True])
+        control = arr[[0, 2, 3]]
+        test = np.ma.compress(cond, arr, axis=0)
+        assert_equal(test, control)
+        marr = np.ma.array(arr)
+        test = np.ma.compress(cond, marr, axis=0)
+        assert_equal(test, control)
+
 #------------------------------------------------------------------------------
 
 class TestMaskedFields(TestCase):