[FIXED] Numpy extract submatrix

Issue

I'm pretty new in numpy and I am having a hard time understanding how to extract from a np.array a sub matrix with defined columns and rows:

Y = np.arange(16).reshape(4,4)

If I want to extract columns/rows 0 and 3, I should have:

[[0 3]
 [12 15]]

I tried all the reshape functions...but cannot figure out how to do this. Any ideas?

Solution

Give np.ix_ a try:

Y[np.ix_([0,3],[0,3])]

This returns your desired result:

In [25]: Y = np.arange(16).reshape(4,4)
In [26]: Y[np.ix_([0,3],[0,3])]
Out[26]:
array([[ 0,  3],
       [12, 15]])

Answered By - JoshAdel