I have two array s
x=array([[0, 0, 0, 0, 0],
[1, 0, 0, 0, 0],
[2, 2, 2, 2, 2]])
I want to subselect elements in each row by the length in array y
y = array([3, 2, 4])
My target is z:
z = array([[0, 0, 0],
[1, 0,],
[2, 2, 2, 2]])
How could I do that with numpy functions instead of list/loop?
Thank you so much for your help.
Numpy array is optimized for homogeneous array with a specific dimensions. I like to think of it like a matrix: it does not make sense to have a matrix with different number of elements on each rows.
That said, depending on how you want to use the processed array, you can simply make a list of array:
z = [array([0, 0, 0]),
array([1, 0,]),
array([2, 2, 2, 2]])]
Still, you will need to do that manually:
x = array([[0, 0, 0, 0, 0], [1, 0, 0, 0, 0], [2, 2, 2, 2, 2]])
y = array([3, 2, 4])
z = [x_item[:y_item] for x_item, y_item in zip(x, y)]
The list comprehension iterates over the x and y combined with zip() to create the new slice of the original array.
Something like this also,
z = [x[i,:e] for i,e in enumerate(y)]
np.splitand discard every other bit.