Closed
Description
When using a structured masked array where one of the structure elements has a multidimensional dtype, indexing does not correctly set the fill_value attribute for the new masked array. This leads to a fill_value with a shape that is incompatible with .data or .mask, which inevitably leads to broadcasting problems when fill_value is used, such as when calling filled():
In [332]: A = ma.masked_array(data=[([0,1,2],), ([3,4,5],)], mask=[([True, False, False],), ([False, True, False],)], dtype=[("A", ">i2", (3,))])
In [339]: A["A"][:, 0].filled()
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-339-ddde509d73bf> in <module>()
----> 1 A["A"][:, 0].filled()
/home/users/gholl/venv/stable-3.5/lib/python3.5/site-packages/numpy/ma/core.py in filled(self, fill_value)
3573 result = self._data.copy('K')
3574 try:
-> 3575 np.copyto(result, fill_value, where=m)
3576 except (TypeError, AttributeError):
3577 fill_value = narray(fill_value, dtype=object)
ValueError: could not broadcast input array from shape (3) into shape (2)
In [341]: A.shape, A.fill_value.shape, A["A"].shape, A["A"].fill_value.shape, A["A"][:, 0].shape, A["A"][:, 0].fill_value.shape
Out[341]: ((2,), (), (2, 3), (3,), (2,), (3,))
Indeed, the fill value doesn't change upon indexing the masked array — only its dtype does:
In [351]: A.fill_value, A["A"].fill_value, A["A"][:, 0].fill_value
Out[351]:
(([16959, 16959, 16959],),
array([16959, 16959, 16959], dtype=int16),
array([16959, 16959, 16959], dtype=int16))