[Numpy-discussion] Fix for ticket #1973

[Charles R Harris]

On Mon, Jan 16, 2012 at 8:52 AM, Charles R Harris <charlesr.harris at gmail.com
> wrote:

>
>
> On Mon, Jan 16, 2012 at 8:37 AM, Bruce Southey <bsouthey at gmail.com> wrote:
>
>> **
>> On 01/14/2012 04:31 PM, Charles R Harris wrote:
>>
>> I've put up a pull request for a fix to ticket #1973. Currently the fix
>> simply propagates the maskna flag when the *.astype method is called. A
>> more complicated option would be to add a maskna keyword to specify whether
>> the output is masked or not or propagates the type of the source, but that
>> seems overly complex to me.
>>
>> Thoughts?
>>
>> Chuck
>>
>>
>> _______________________________________________
>> NumPy-Discussion mailing listNumPy-Discussion at scipy.orghttp://mail.scipy.org/mailman/listinfo/numpy-discussion
>>
>>  Thanks for the correction and as well as the fix. While it worked for
>> integer and floats (not complex ones), I got an error when using complex
>> dtypes. This error that is also present in array creation of complex
>> dtypes. Is this known or a new bug?
>>
>> If it is new, then we need to identify what functionality should handle
>> np.NA but are not working.
>>
>> Bruce
>>
>> $ python
>> Python 2.7 (r27:82500, Sep 16 2010, 18:02:00)
>> [GCC 4.5.1 20100907 (Red Hat 4.5.1-3)] on linux2
>> Type "help", "copyright", "credits" or "license" for more information.
>> >>> import numpy as np
>> >>> np.__version__ # pull request version
>> '2.0.0.dev-88f9276'
>> >>> np.array([1,2], dtype=np.complex)
>> array([ 1.+0.j,  2.+0.j])
>> >>> np.array([1,2, np.NA], dtype=np.complex)
>> Traceback (most recent call last):
>>   File "<stdin>", line 1, in <module>
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/numeric.py", line
>> 1445, in array_repr
>>     ', ', "array(")
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/arrayprint.py",
>> line 459, in array2string
>>     separator, prefix, formatter=formatter)
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/arrayprint.py",
>> line 263, in _array2string
>>     suppress_small),
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/arrayprint.py",
>> line 724, in __init__
>>     self.real_format = FloatFormat(x.real, precision, suppress_small)
>> ValueError: Cannot construct a view of data together with the
>> NPY_ARRAY_MASKNA flag, the NA mask must be added later
>> >>> ca=np.array([1,2], dtype=np.complex, maskna=True)
>> >>> ca[1]=np.NA
>> >>> ca
>> Traceback (most recent call last):
>>   File "<stdin>", line 1, in <module>
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/numeric.py", line
>> 1445, in array_repr
>>     ', ', "array(")
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/arrayprint.py",
>> line 459, in array2string
>>     separator, prefix, formatter=formatter)
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/arrayprint.py",
>> line 263, in _array2string
>>     suppress_small),
>>   File "/usr/lib64/python2.7/site-packages/numpy/core/arrayprint.py",
>> line 724, in __init__
>>     self.real_format = FloatFormat(x.real, precision, suppress_small)
>> ValueError: Cannot construct a view of data together with the
>> NPY_ARRAY_MASKNA flag, the NA mask must be added later
>> >>>
>>
>>
> Looks like a different bug involving the *.real and *.imag views. I'll
> take a look.
>
>
Looks like views of masked arrays have other problems:

In [13]: a = ones(3, int16, maskna=1)

In [14]: a.view(int8)
Out[14]: array([1, 0, 1, NA, 1, NA], dtype=int8)


I'm not sure what the policy should be here. One could construct a new mask
adapted to the view, raise an error when the types don't align (I think the
real/imag parts should be considered aligned), or just let the view unmask
the array. The last seems dangerous. Hmm...

Chuck
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