2D index of numpy array using array indexing [duplicate]

Question

If I have a 2D array of indices:

i = np.array([[0, 0], [1, 1]])

And a 2D array I want to index:

a = np.array([[1, 2], [3, 4]])

How can I index the array to get a 1D array like the following?

np.array([1, 4])

llllllllll · Accepted Answer · 2018-03-01 18:45:46Z

3

You can use:

a[i.T[0], i.T[1]]

In case you have more dimensions, you can use:

a[tuple(i.T)]

answered Mar 1, 2018 at 18:36

llllllllll

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Comments

Kasravnd · Accepted Answer · 2018-03-01 18:44:20Z

0

You just need a simple indexing:

In [11]: a[i[:, 0], i[:, 1]]
Out[11]: array([1, 4])

The first column of i is number of rows and the second one denotes the column number.

answered Mar 1, 2018 at 18:44

Kasravnd

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