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pythonarrayspython-3.xnumpyaverage

Adding a numpy array to another which has different dimensions

I have an empty numpy array (let's call it a), which is for example (1200, 1000) in size.

There are several numpy arrays that I want to get sum of them and save them in the array a.

The size of these arrays (b_i) are like (1200, y), and y is max=1000.

Simply writing a code such as:

a = a + b_i

didn't work because of second dimension mismatch.

How can I solve that?

Solution

  • If you just want to concatinate arrays:

    a = np.ones((1200,1000))
b = np.ones((1200, 500))
c = np.concatenate((a, b), axis=1)
c.shape # == (1200, 1500)

    If you want elementwise addition, then reshape b to have the same dimentions as a

    a = np.ones((1200,1000))
b = np.ones((1200, 500))
b_pad = np.zeros(a.shape)
b_pad[:b.shape[0],:b.shape[1]] = b
a + b_pad

    array([[2., 2., 2., ..., 1., 1., 1.],
       [2., 2., 2., ..., 1., 1., 1.],
       [2., 2., 2., ..., 1., 1., 1.],
       ...,
       [2., 2., 2., ..., 1., 1., 1.],
       [2., 2., 2., ..., 1., 1., 1.],
       [2., 2., 2., ..., 1., 1., 1.]])

    If you want a reusable function for this, then have a look at this question