[Numpy-discussion] nan_to_num and bool arrays

Keith Goodman kwgoodman@gmail....
Fri Dec 11 14:41:02 CST 2009


On Fri, Dec 11, 2009 at 12:08 PM, Bruce Southey <bsouthey@gmail.com> wrote:
> On 12/11/2009 01:33 PM, Robert Kern wrote:
>> On Fri, Dec 11, 2009 at 13:11, Bruce Southey<bsouthey@gmail.com>  wrote:
>>
>>
>>> As documented, nan_to_num returns a float so it does not return the
>>> input unchanged.
>>>
> Sorry for my mistake:
> Given an int input, np.nan_to_num returns an int dtype
>  >>> np.nan_to_num(np.zeros((3,3), dtype=np.int)).dtype
> dtype('int64')
>
>> I think that is describing the current behavior rather than
>> documenting the intent of the function. Given the high level purpose
>> of the function, to "[r]eplace nan with zero and inf with finite
>> numbers," I think it is fairly reasonable to implement it as a no-op
>> for integers and related dtypes. There are no nans or infs for those
>> dtypes so the input can be passed back unchanged.
>>
>
> So I agree that it should leave the input untouched when a non-float
> dtype is used for some array-like input.

Would only one line need to be changed? Would changing

if not issubclass(t, _nx.integer):

to

if not issubclass(t, _nx.integer) and not issubclass(t, _nx.bool_):

do the trick?

Here's nan_to_num for reference:

def nan_to_num(x):
    try:
        t = x.dtype.type
    except AttributeError:
        t = obj2sctype(type(x))
    if issubclass(t, _nx.complexfloating):
        return nan_to_num(x.real) + 1j * nan_to_num(x.imag)
    else:
        try:
            y = x.copy()
        except AttributeError:
            y = array(x)
    if not issubclass(t, _nx.integer):
        if not y.shape:
            y = array([x])
            scalar = True
        else:
            scalar = False
        are_inf = isposinf(y)
        are_neg_inf = isneginf(y)
        are_nan = isnan(y)
        maxf, minf = _getmaxmin(y.dtype.type)
        y[are_nan] = 0
        y[are_inf] = maxf
        y[are_neg_inf] = minf
        if scalar:
            y = y[0]
    return y


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