Mann-Kendall Statistic

Problem

Compute the Mann-Kendall trend statistic S = sum over i < j of sign(series[j] - series[i]), counting +1 for increases and -1 for decreases.

Positive S indicates an upward trend, negative S a downward trend, and 0 no monotone tendency.

Hint

It is a nonparametric test: only the signs of pairs matter, not magnitudes.

case 1

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

expected: 6

case 2

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

expected: -6

case 3

in: [[1,3,2]]

expected: 1

case 4

in: [[5,5,5]]

expected: 0

Starter codePython

def mann_kendall_statistic(series):
    # Your code here
    pass

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