CUSUM Statistic

Problem

Compute the cumulative sum control chart values for a series around a target: S[t] = sum over i <= t of (x[i] - target).

Return the running sums as a list; an empty series gives an empty list.

Hint

A drift in the CUSUM away from zero signals a change in level.

case 1

in: [[1,2,3,4],2]

expected: [-1,-1,0,2]

case 2

in: [[5,5,5],5]

expected: [0,0,0]

case 3

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

expected: [1,3,6]

case 4

in: [[],1]

expected: []

Starter codePython

def cusum(series, target):
    # Your code here
    pass

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