[Numpy-discussion] Behaviour of integer powers

josef.pktd@gmai... josef.pktd@gmai...
Sun Feb 8 07:19:08 CST 2009


On Sun, Feb 8, 2009 at 8:02 AM,  <josef.pktd@gmail.com> wrote:

> But I just found that nan in the exponent in an array are not propagated:
>
>>>> 0.0 ** np.array([-np.nan, 0, 1], dtype=np.int32)[0]
> 1.0
>>>> np.power(0.0, np.array([-np.nan, 0, 1], dtype=np.int32)[0])
> 1.0

correction:
np.power propagates nans, it's again the casting of nan to zero int,
that tripped me up.

I shouln't cut and paste examples too fast.

>>> np.power(0.0, np.array([-np.nan, 0, 1]))
array([ NaN,   1.,   0.])
>>> np.power(0.0, np.array([-np.nan, 0, 1]))[0]
1.#QNAN

Josef


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