[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
> 
> 
> _______________________________________________
> NumPy-Discussion mailing list
> NumPy-Discussion at scipy.org
> http://mail.scipy.org/mailman/listinfo/numpy-discussion





More information about the NumPy-Discussion mailing list