Convert a 1D array to a 2D array in numpy

python arrays matrix numpy multidimensional-array
ahwillia picture ahwillia · Sep 25, 2012 · Viewed 302.3k times · Source

I want to convert a 1-dimensional array into a 2-dimensional array by specifying the number of columns in the 2D array. Something that would work like this:

> import numpy as np
> A = np.array([1,2,3,4,5,6])
> B = vec2matrix(A,ncol=2)
> B
array([[1, 2],
       [3, 4],
       [5, 6]])

Does numpy have a function that works like my made-up function "vec2matrix"? (I understand that you can index a 1D array like a 2D array, but that isn't an option in the code I have - I need to make this conversion.)

Answer

Matt Ball picture Matt Ball · Sep 25, 2012

You want to reshape the array.

B = np.reshape(A, (-1, 2))

where -1 infers the size of the new dimension from the size of the input array.

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