[FIXED] NumPy elementwise chaining comparison (a <= b <= c)

Issue

Python support chaining comparison:

1<2<3<4

How to do that for NumPy?

If only 3 array, we can do this:

a = np.array([1,2,4,5,6])
b = np.array([2,6,1,5,6])
c = np.array([7,4,6,6,8])
np.logical_and((a <= b),(b <= c))

With 4 array, it becomes too burdensome since np.logical_and only accept 2 inputs.

a = np.array([1,2,4,5,6])
b = np.array([2,6,1,5,6])
c = np.array([7,4,6,6,8])
d = np.array([8,9,9,9,2])
np.logical_and((a <= b),(b <= c))  # work
np.logical_and((b <= c),(c <= d))  # work
np.logical_and((a <= b),(b <= c),(c <= d))  # not work

---

Edit: Slightly add complexity, on 2D:

a = np.array([[1,2,3],
              [4,5,6]])
b = np.array([[2,6,3],
              [1,5,6]])
c = np.array([[7,4,3],
              [6,6,8]])
d = np.array([[8,9,3],
              [9,9,2]])

Solution

Simply use &:

(a <= b) & (b <= c) & (c <= d)

As the doc says:

The & operator can be used as a shorthand for np.logical_and on boolean ndarrays.

Answered By - Kelly Bundy