Proximal Operator of Box

Problem

The proximal operator of the indicator function of the box [lo, hi] is the projection onto that box, which is elementwise clipping.

Given a list of values and bounds lo <= hi, return [max(lo, min(hi, v)) for each v].

Hint

Projection onto a box clips every coordinate independently.

case 1

in: [[-2,0.5,3],0,1]

expected: [0,0.5,1]

case 2

in: [[5,5],-1,1]

expected: [1,1]

case 3

in: [[0.2,0.8],0.3,0.7]

expected: [0.3,0.7]

case 4

in: [[],0,1]

expected: []

Starter codePython

def prox_box(values, lo, hi):
    # Your code here
    pass

4 test cases · run your code against them in the editor