I have a list of tuples: [(0,0), (1,1), (2,2), (3,3), (4,4)]
And I have my 2d numpy array:
array([[8, 6, 5, 9, 3],
[7, 9, 7, 9, 1],
[2, 1, 8, 8, 6],
[7, 1, 5, 1, 3],
[6, 7, 1, 1, 5]])
How can I get the values from the 2d array located by using the positions from the list with numpy?
I should get the diagonal: [8,9,8,1,5]
You can transpose the list of tuples, and pass these as items in a tuple:
>>> b = [(0, 0), (1, 1), (2, 2), (3, 3), (4, 4)]
>>> a[tuple(np.transpose(b))]
array([8, 9, 8, 1, 5])
Try this,
>>> import numpy as np
>>> req_index = [(0,0), (1,1), (2,2), (3,3), (4,4)] # this is your tuple index list
>>> arr = np.array([[8, 6, 5, 9, 3],
[7, 9, 7, 9, 1],
[2, 1, 8, 8, 6],
[7, 1, 5, 1, 3],
[6, 7, 1, 1, 5]])
>>>
Output:
>>> [arr[i][j] for i, j in req_index]
[8, 9, 8, 1, 5]
Here's one way to do this:
a=np.array([[8, 6, 5, 9, 3],
[7, 9, 7, 9, 1],
[2, 1, 8, 8, 6],
[7, 1, 5, 1, 3],
[6, 7, 1, 1, 5]])
np.diag(a)
prints array([8, 9, 8, 1, 5]).
([0,1,2,3],[0,1,2,3])