I've read documentation several times about np.indices() but I can't seem to grasp what is it about. I've used it numerous times on things to see what it does, but I still can't really get it. Maybe the thing is I'm a beginner in programming so I can't understand the idea behind the words describing it. In addition I'm not a native English speaker (though I have no problems with it). I would be very grateful for kind of easier explanation, possibly on some example. Thanks.
Suppose you have a matrix M whose (i,j)-th element equals
M_ij = 2*i + 3*j
One way to define this matrix would be
i, j = np.indices((2,3))
M = 2*i + 3*j
which yields
array([[0, 3, 6],
[2, 5, 8]])
In other words, np.indices returns arrays which can be used as indices. The elements in i indicate the row index:
In [12]: i
Out[12]:
array([[0, 0, 0],
[1, 1, 1]])
The elements in j indicate the column index:
In [13]: j
Out[13]:
array([[0, 1, 2],
[0, 1, 2]])