How would you go about reshaping a length-N 1D array into an (N/2) x 2 array? In numpy, for example, you can use -1 in place of N/2 when reshaping:
>>> x = np.array([1,2,3,4])
>>> x.reshape((-1, 2))
array([[1, 2],
[3, 4]])
So I'm wondering if there's a J equivalent. It feels clunky to explicitly calculate the required number of rows.
This is what infix (\) is for: n ,\y will ravel (,) every n items ("infixes" of length n). If n is negative the infixes are non overlapping.
y =. i.20
_2 ,\y
0 1
2 3
4 5
6 7
8 9
10 11
12 13
14 15
16 17
18 19
_3 ,\y
0 1 2
3 4 5
6 7 8
9 10 11
12 13 14
15 16 17
18 19 0