Replace values in bigger numpy array with smaller array

Question

I have 2 numpy arrays: The bigger one is a 10 x 10 numpy array and the smaller one is a 2 x 2 array.

I would like to substitute the values in the bigger array with those from the smaller array, at a user specified location. E.g. Replace the values of the 10 x 10 array starting from its center point by replacing 4 values with the 2 x 2 array.

Right now, I am doing this by using a nested for loop, and figuring out which pixels in the bigger array overlap those of the smaller array. Is there a more pythonic way to do it?

Akavall · Accepted Answer · 2016-01-13 23:12:40Z

7

In [1]: import numpy as np

In [2]: a = np.zeros(100).reshape(10,10)

In [3]: b = np.ones(4).reshape(2,2)

In [4]: a[4:6, 4:6] = b

In [5]: a
Out[5]: 
array([[ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  1.,  1.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  1.,  1.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.],
       [ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.]])

answered Jan 13, 2016 at 23:12

Akavall

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