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charris opened this issue May 2, 2015 · 2 comments
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ma.where does not work with structured types. #5826

charris opened this issue May 2, 2015 · 2 comments
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00 - Bug component: numpy.ma masked arrays

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@charris
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charris commented May 2, 2015

I think this is an easy fix for someone familiar with the ma module.

In [1]: x = np.ones(3, dtype=[('a', 'i4'), ('b', 'f4')]).view(ma.MaskedArray)

In [2]: y = np.zeros(3, dtype=[('a', 'i4'), ('b', 'f4')]).view(ma.MaskedArray)

In [3]: ma.where([True, False, True], x, y)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-3-5e3a8c327920> in <module>()
----> 1 ma.where([True, False, True], x, y)

/home/charris/.local/lib/python2.7/site-packages/numpy/ma/core.pyc in where(condition, x, y)
   6786     # Create an empty mask and fill it
   6787     mask = np.zeros(fc.shape, dtype=MaskType)
-> 6788     np.copyto(mask, getmask(x), where=fc)
   6789     np.copyto(mask, getmask(y), where=notfc)
   6790     mask |= getmaskarray(condition)

TypeError: Cannot cast scalar from dtype([('a', '?'), ('b', '?')]) to dtype('bool') according to the rule 'same_kind'
charris added a commit to charris/numpy that referenced this issue May 2, 2015
@charris
BUG: Make ma.where work with structured types.
ad85c47 
Closes numpy#5826.
@charris charris mentioned this issue May 2, 2015
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@githubmlai
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Not easy fix?

It might have to use result_type in where function

    if x is masked:
        ndtype = yv.dtype
    elif y is masked:
        ndtype = xv.dtype
    else:
        ndtype = np.result_type(xv.dtype, yv.dtype)

might help but cause further error because you can't do OR operation on structured mask

e.g.

    _mask |= getmaskarray(condition)

throws error

@njsmith njsmith removed the Easy Fix label Jul 12, 2015
@eric-wieser
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eric-wieser commented Sep 27, 2017 •
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This is fixed in 1.14-dev:

masked_array(data = [(1, 1.0) (0, 0.0) (1, 1.0)],
             mask = [(False, False) (False, False) (False, False)],
       fill_value = (999999, 1.00000002e+20),
            dtype = [('a', '<i4'), ('b', '<f4')])

Edit: #8647

@eric-wieser eric-wieser mentioned this issue Sep 27, 2017
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BUG: Make ma.where work with structured types. charris/numpy
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@charris @eric-wieser @njsmith @githubmlai