Python/maths/sigmoid.py

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"""
This script demonstrates the implementation of the Sigmoid function.
The function takes a vector of K real numbers as input and then 1 / (1 + exp(-x)).
After through Sigmoid, the element of the vector mostly 0 between 1. or 1 between -1.
Script inspired from its corresponding Wikipedia article
https://en.wikipedia.org/wiki/Sigmoid_function
"""
import numpy as np
def sigmoid(vector: np.array) -> np.array:
"""
Implements the sigmoid function
Parameters:
vector (np.array): A numpy array of shape (1,n)
consisting of real values
Returns:
sigmoid_vec (np.array): The input numpy array, after applying
sigmoid.
Examples:
>>> sigmoid(np.array([-1.0, 1.0, 2.0]))
array([0.26894142, 0.73105858, 0.88079708])
>>> sigmoid(np.array([0.0]))
array([0.5])
"""
return 1 / (1 + np.exp(-vector))
if __name__ == "__main__":
import doctest
doctest.testmod()