How do I find a matrix of all sums of two arrays?
With the input
x1 = np.array([0, 1])
x2 = np.array([1,2,3])
I want the output of this to be like this:
[[1, 2, 3], [2, 3, 4]]
2 Answers
You can use NumPy's newaxis attribute:
x1[:, np.newaxis] + x2
which is an acronym for None:
In [2]: np.newaxis is None
Out[2]: True
Thus:
x1[:, None] + x2
also works.
answered Jun 3, 2017 at 9:00
Saullo G. P. Castro
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Comments
You can use list comprehension like this example:
x1 = np.array([0, 1])
x2 = np.array([1,2,3])
final = [[j+k for j in x2] for k in x1]
# Or, maybe:
# final = np.array([[j+k for j in x2] for k in x1])
# >>> array([[1, 2, 3], [2, 3, 4]])
print(final)
Output:
[[1, 2, 3], [2, 3, 4]]
x1[:,None]+x2.