Seasonal Shift Detect

Problem

Detect a change in the seasonal pattern. Split the series in half, average each season position (index modulo period) within each half, and return True when any position's mean differs by more than threshold between the halves.

Return False for invalid periods or when the series is shorter than two full periods.

Hint

Comparing per-position means isolates a change in seasonality from a level shift.

Test cases

case 1

in: [[1,5,1,5,1,5,1,5],2,0.5]

expected: false

case 2

in: [[1,2,1,2,5,6,5,6],2,1]

expected: true

case 3

in: [[1,2,3,4],2,10]

expected: false

case 4

in: [[1,2,1,2,3,4,3,4],2,0.5]

expected: true

Starter codePython

def seasonal_shift_detect(series, period, threshold):
    # Your code here
    pass

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