How To Specify The Last Index Explicitly To Np.ufunc.reduceat

Say I have an array data = np.arange(6) I want to find the sum of the entire array and the second half using np.add.reduceat.1 If I do it like this: np.add.reduceat(data, [0, 6, 3

Solution 1:

I haven't used reduceat much, but it looks like you can only have one open ended range, one add to the end.

One way around that is to pad the array (yes, I do normally rail against using np.append :) ):

In [165]: np.add.reduceat(np.append(x,0),[0,6,3])
Out[165]: array([15,  0, 12])

or with a full pairing of ranges:

In [166]: np.add.reduceat(np.append(x,0),[0,6,3,6])
Out[166]: array([15,  0, 12,  0])

I omitted the usual [::2] to clarify what is going on.