I would like to create a matrix of pairwise arrays from two arrays of different length, a and b:
a = np.array([1,2,3])
b = np.array([4,5,6,7])
So, c matrix should look like:
[[1,4], [1,5], [1,6], ..., [3,7]]
4 Answers
c = [[i,j] for i in (a) for j in (b)]
1 Comment
mx0
While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value.
You can use np.meshgrid().
a = np.array((1, 2, 3))
b = np.array((4, 5, 6, 7))
out = np.stack([each.ravel(order='F') for each in np.meshgrid(a, b)])
out now looks like this:
array([[1, 4],
[1, 5],
[1, 6],
[1, 7],
[2, 4],
[2, 5],
[2, 6],
[2, 7],
[3, 4],
[3, 5],
[3, 6],
[3, 7]])
1 Comment
user3932000
Why use
order='F'?You can also use product from itertools library. product(a, b) will return iterator product between a and b. Using vstack to make it an array.
from itertools import product
np.vstack(product(a, b))
Output
array([[1, 4], [1, 5], [1, 6], ...])
Comments
You can create a 2D numpy array with your two arrays and then swap the axes of the combined array with np.swapaxes to acquire shape you want.
X = np.array([a, b])
swapped_array = X.swapaxes(1,0)
# X.swapaxes(0,1) returns the same result
npobject?