Log Transform Series

Problem

Apply the natural logarithm elementwise to a series, a standard variance-stabilizing transform for data that grows multiplicatively.

Return 0.0 for any non-positive value, since the logarithm is undefined there.

Hint

Import the math module and guard against x <= 0.

case 1

in: [[1,10,100]]

expected: [0,2.302585092994046,4.605170185988092]

case 2

in: [[0,1]]

expected: [0,0]

case 3

in: [[2.718281828459045]]

expected: [1]

case 4

in: [[0.5]]

expected: [-0.6931471805599453]

Starter codePython

import math
def log_transform(series):
    # Your code here
    pass

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