[Numpy-discussion] accumulation operation
Sebastian Berg
sebastian at sipsolutions.net
Wed Jan 22 12:32:15 EST 2014
On Wed, 2014-01-22 at 17:23 +0000, Ralf Juengling wrote:
> Executing the following code,
>
>
>
> >>> import numpy as np
>
> >>> a = np.zeros((3,))
>
> >>> w = np.array([0, 1, 0, 1, 2])
>
> >>> v = np.array([10.0, 1, 10.0, 2, 9])
>
> >>> a[w] += v
>
>
>
> I was expecting ‘a’ to be array([20., 3., 9.]. Instead I get
>
>
>
> >>> a
>
> array([ 10., 2., 9.])
>
>
>
> This with numpy version 1.6.1.
>
> Is there another way to do the accumulation I want?
>
>
Since you have addition, you should use np.bincount
- Sebastian
>
> Thanks,
> Ralf
>
>
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