[Numpy-discussion] numpy.nansum() behavior in 1.3.0
josef.pktd at gmail.com
josef.pktd at gmail.com
Mon Jun 1 14:34:49 EDT 2009
On Mon, Jun 1, 2009 at 2:26 PM, Keith Goodman <kwgoodman at gmail.com> wrote:
> On Mon, Jun 1, 2009 at 11:16 AM, <josef.pktd at gmail.com> wrote:
>> On Mon, Jun 1, 2009 at 1:43 PM, Keith Goodman <kwgoodman at gmail.com> wrote:
>>> On Mon, Jun 1, 2009 at 9:55 AM, Michael Hearne <mhearne at usgs.gov> wrote:
>>>> A question (and possibly a bug):
>>>>
>>>> What should be returned when I do:
>>>>
>>>> numpy.nansum([])
>>>>
>>>> In my copy of numpy 1.1.1, I get 0.0. This is what I would expect to
>>>> see.
>>>> However, this behavior seems to have changed in 1.3.0, in which I get
>>>> nan.
>>>
>>> Here's a weird one. This is in numpy 1.2:
>>>
>>>>> np.sum(9)
>>> 9
>>>>> np.sum(9.0)
>>> 9.0
>>>>> np.nansum(9)
>>> 9
>>>>> np.nansum(9.0)
>>> ---------------------------------------------------------------------------
>>> IndexError: 0-d arrays can't be indexed.
>>
>> wrong argument in isnan, I think
>>
>> Josef
>>
>> In file: C:\Programs\Python25\Lib\site-packages\numpy\lib\function_base.py
>>
>> def _nanop(op, fill, a, axis=None):
>> """
>> ...
>>
>> """
>> y = array(a,subok=True)
>> - mask = isnan(a)
>> + mask = isnan(y)
>> if mask.all():
>> return np.nan
>>
>> if not issubclass(y.dtype.type, np.integer):
>> y[mask] = fill
>>
>> return op(y, axis=axis)
>
> The problem I came across, np.nansum(float), is caused by this line
>
> y[mask] = fill
>
> when y is 0-d.
if mask is an array then this works, my initial solution was mask =
np.array(mask). then I thought it works also the other way, but it
doesn't. I shouldn't have changed my mind
>>> y
array(9.0)
>>> y[np.array(np.isnan(9))] = 0
>>> y
array(9.0)
>>> y[np.isnan(np.array(9))] = 0
Traceback (most recent call last):
File "<pyshell#45>", line 1, in <module>
y[np.isnan(np.array(9))] = 0
IndexError: 0-d arrays can't be indexed.
Josef
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