Merge pull request #10223 from lzkelley/ma-stack-10127

ENH: added masked version of 'numpy.stack' with tests.

2 files changed, 85 insertions, 2 deletions

diff --git a/numpy/ma/extras.py b/numpy/ma/extras.py
index 323fbce38..360d50d8a 100644
--- a/numpy/ma/extras.py
+++ b/numpy/ma/extras.py
@@ -19,7 +19,7 @@ __all__ = [
     'hsplit', 'hstack', 'isin', 'in1d', 'intersect1d', 'mask_cols', 'mask_rowcols',
     'mask_rows', 'masked_all', 'masked_all_like', 'median', 'mr_',
     'notmasked_contiguous', 'notmasked_edges', 'polyfit', 'row_stack',
-    'setdiff1d', 'setxor1d', 'unique', 'union1d', 'vander', 'vstack',
+    'setdiff1d', 'setxor1d', 'stack', 'unique', 'union1d', 'vander', 'vstack',
     ]
 
 import itertools
@@ -357,6 +357,7 @@ vstack = row_stack = _fromnxfunction_seq('vstack')
 hstack = _fromnxfunction_seq('hstack')
 column_stack = _fromnxfunction_seq('column_stack')
 dstack = _fromnxfunction_seq('dstack')
+stack = _fromnxfunction_seq('stack')
 
 hsplit = _fromnxfunction_single('hsplit')
 
diff --git a/numpy/ma/tests/test_extras.py b/numpy/ma/tests/test_extras.py
index af9f42c2a..7687514fa 100644
--- a/numpy/ma/tests/test_extras.py
+++ b/numpy/ma/tests/test_extras.py
@@ -29,7 +29,7 @@ from numpy.ma.extras import (
     ediff1d, apply_over_axes, apply_along_axis, compress_nd, compress_rowcols,
     mask_rowcols, clump_masked, clump_unmasked, flatnotmasked_contiguous,
     notmasked_contiguous, notmasked_edges, masked_all, masked_all_like, isin,
-    diagflat
+    diagflat, stack, vstack, hstack
     )
 import numpy.ma.extras as mae
 
@@ -1589,5 +1589,87 @@ class TestShapeBase(object):
         assert_equal(b.mask.shape, b.data.shape)
 
 
+class TestStack(object):
+
+    def test_stack_1d(self):
+        a = masked_array([0, 1, 2], mask=[0, 1, 0])
+        b = masked_array([9, 8, 7], mask=[1, 0, 0])
+
+        c = stack([a, b], axis=0)
+        assert_equal(c.shape, (2, 3))
+        assert_array_equal(a.mask, c[0].mask)
+        assert_array_equal(b.mask, c[1].mask)
+
+        d = vstack([a, b])
+        assert_array_equal(c.data, d.data)
+        assert_array_equal(c.mask, d.mask)
+
+        c = stack([a, b], axis=1)
+        assert_equal(c.shape, (3, 2))
+        assert_array_equal(a.mask, c[:, 0].mask)
+        assert_array_equal(b.mask, c[:, 1].mask)
+
+    def test_stack_masks(self):
+        a = masked_array([0, 1, 2], mask=True)
+        b = masked_array([9, 8, 7], mask=False)
+
+        c = stack([a, b], axis=0)
+        assert_equal(c.shape, (2, 3))
+        assert_array_equal(a.mask, c[0].mask)
+        assert_array_equal(b.mask, c[1].mask)
+
+        d = vstack([a, b])
+        assert_array_equal(c.data, d.data)
+        assert_array_equal(c.mask, d.mask)
+
+        c = stack([a, b], axis=1)
+        assert_equal(c.shape, (3, 2))
+        assert_array_equal(a.mask, c[:, 0].mask)
+        assert_array_equal(b.mask, c[:, 1].mask)
+
+    def test_stack_nd(self):
+        # 2D
+        shp = (3, 2)
+        d1 = np.random.randint(0, 10, shp)
+        d2 = np.random.randint(0, 10, shp)
+        m1 = np.random.randint(0, 2, shp).astype(bool)
+        m2 = np.random.randint(0, 2, shp).astype(bool)
+        a1 = masked_array(d1, mask=m1)
+        a2 = masked_array(d2, mask=m2)
+
+        c = stack([a1, a2], axis=0)
+        c_shp = (2,) + shp
+        assert_equal(c.shape, c_shp)
+        assert_array_equal(a1.mask, c[0].mask)
+        assert_array_equal(a2.mask, c[1].mask)
+
+        c = stack([a1, a2], axis=-1)
+        c_shp = shp + (2,)
+        assert_equal(c.shape, c_shp)
+        assert_array_equal(a1.mask, c[..., 0].mask)
+        assert_array_equal(a2.mask, c[..., 1].mask)
+
+        # 4D
+        shp = (3, 2, 4, 5,)
+        d1 = np.random.randint(0, 10, shp)
+        d2 = np.random.randint(0, 10, shp)
+        m1 = np.random.randint(0, 2, shp).astype(bool)
+        m2 = np.random.randint(0, 2, shp).astype(bool)
+        a1 = masked_array(d1, mask=m1)
+        a2 = masked_array(d2, mask=m2)
+
+        c = stack([a1, a2], axis=0)
+        c_shp = (2,) + shp
+        assert_equal(c.shape, c_shp)
+        assert_array_equal(a1.mask, c[0].mask)
+        assert_array_equal(a2.mask, c[1].mask)
+
+        c = stack([a1, a2], axis=-1)
+        c_shp = shp + (2,)
+        assert_equal(c.shape, c_shp)
+        assert_array_equal(a1.mask, c[..., 0].mask)
+        assert_array_equal(a2.mask, c[..., 1].mask)
+
+
 if __name__ == "__main__":
     run_module_suite()