Fourier Features

Problem

Build Fourier features at time t: for harmonics h = 1..harmonics append sin(2*pi*h*t/period) and cos(2*pi*h*t/period).

Return an empty list when period is not positive or harmonics < 1. Fourier terms let linear models fit smooth seasonality.

Hint

Each harmonic contributes a sine-cosine pair, so the vector length is 2 * harmonics.

case 1

in: [0,4,2]

expected: [0,1,0,1]

case 2

in: [1,4,1]

expected: [1,6.123233995736766e-17]

case 3

in: [1,4,2]

expected: [1,6.123233995736766e-17,1.2246467991473532e-16,-1]

case 4

in: [0,0,2]

expected: []

Starter codePython

import math
def fourier_features(t, period, harmonics):
    # Your code here
    pass

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