Theta Method Forecast

Problem

Compute the theta method forecast h steps ahead: the SES forecast with smoothing factor alpha plus 0.5 * h * slope, where slope is the OLS slope of the series on time.

Return 0.0 for an empty series; a single point has slope 0.

Hint

The theta method blends exponential smoothing with half the linear trend.

Test cases

case 1

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

expected: 3.625

case 2

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

expected: 4.125

case 3

in: [[5,5,5],0.3,1]

expected: 5

case 4

in: [[10],0.7,3]

expected: 10

Starter codePython

def theta_method_forecast(series, alpha, h):
    # Your code here
    pass

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