[FIXED] Allocate array with values and indices from other arrays

Issue

I have 2 arrays, one with values and the other with indices. Can I populate another array (with different dimensions) using these two in numpy?

vals = [[0.7, 0.7, 0.2, 0.1], 
        [0.3, 0.2, 0.1, 0.1]]
indices = [[2, 5, 6, 8], 
           [0, 1, 2, 7]]
required_array = [[0, 0, 0.7, 0, 0, 0.7, 0.2, 0, 0.1], 
                  [0.3, 0.2, 0.1, 0, 0, 0, 0, 0.1, 0]]          

Note that the values for the indexes that aren't present in the indices array (like 0,1,3,...) are filled with 0.

Solution

First allocate an all zero array, then set the value:

>>> ar = np.zeros(np.max(indices) + 1)
>>> ar[indices] = vals
>>> ar
array([0. , 0. , 0.7, 0. , 0. , 0.7, 0.2, 0. , 0.1])

2d example:

>>> ar = np.zeros((len(indices), np.max(indices) + 1))
>>> ar[np.arange(len(indices))[:, None], indices] = vals
>>> ar
array([[0. , 0. , 0.7, 0. , 0. , 0.7, 0.2, 0. , 0.1],
       [0.3, 0.2, 0.1, 0. , 0. , 0. , 0. , 0.1, 0. ]])

Answered By - Mechanic Pig