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?

Thanks,
Ralf