Have numpy argsort return an array of 2d indices?

Question

If we have a 1d array

arr = np.random.randint(7, size=(5))
# [3 1 4 6 2]
print np.argsort(arr)
# [1 4 0 2 3] <= The indices in the sorted order    
         


        

Answer 1

From the documentation on numpy.argsort:

ind = np.unravel_index(np.argsort(x, axis=None), x.shape)

Indices of the sorted elements of a N-dimensional array.

An example:

>>> x = np.array([[0, 3], [2, 2]])
>>> x
array([[0, 3],
       [2, 2]])
>>> ind = np.unravel_index(np.argsort(x, axis=None), x.shape)
>>> ind # a tuple of arrays containing the indexes
(array([0, 1, 1, 0]), array([0, 0, 1, 1]))
>>> x[ind]  # same as np.sort(x, axis=None)
array([0, 2, 2, 3])enter code here