Concat two arrays of different dimensions numpy

Question

I am trying to concatenate two numpy arrays to add an extra column: array_1 is (569, 30) and array_2 is is (569, )

combined = np.concatenate((array_1, array_2), axis=1)

I thought this would work if I set axis=2 so it will concatenate vertically. The end should should be a 569 x 31 array.

The error I get is ValueError: all the input arrays must have same number of dimensions

Can someone help?

Thx!

Answer 1

You can use numpy.column_stack:

np.column_stack((array_1, array_2))

Which converts the 1-d array to 2-d implicitly, and thus equivalent to np.concatenate((array_1, array_2[:,None]), axis=1) as commented by @umutto.

---

a = np.arange(6).reshape(2,3)
b = np.arange(2)

a
#array([[0, 1, 2],
#       [3, 4, 5]])

b
#array([0, 1])

np.column_stack((a, b))
#array([[0, 1, 2, 0],
#       [3, 4, 5, 1]])