diff --git a/maths/tanh.py b/maths/tanh.py new file mode 100644 index 000000000..ddab3e1ab --- /dev/null +++ b/maths/tanh.py @@ -0,0 +1,42 @@ +""" +This script demonstrates the implementation of the tangent hyperbolic +or tanh function. + +The function takes a vector of K real numbers as input and +then (e^x - e^(-x))/(e^x + e^(-x)). After through tanh, the +element of the vector mostly -1 between 1. + +Script inspired from its corresponding Wikipedia article +https://en.wikipedia.org/wiki/Activation_function +""" +import numpy as np + + +def tangent_hyperbolic(vector: np.array) -> np.array: + """ + Implements the tanh function + + Parameters: + vector: np.array + + Returns: + tanh (np.array): The input numpy array after applying tanh. + + mathematically (e^x - e^(-x))/(e^x + e^(-x)) can be written as (2/(1+e^(-2x))-1 + + Examples: + >>> tangent_hyperbolic(np.array([1,5,6,-0.67])) + array([ 0.76159416, 0.9999092 , 0.99998771, -0.58497988]) + + >>> tangent_hyperbolic(np.array([8,10,2,-0.98,13])) + array([ 0.99999977, 1. , 0.96402758, -0.7530659 , 1. ]) + + """ + + return (2 / (1 + np.exp(-2 * vector))) - 1 + + +if __name__ == "__main__": + import doctest + + doctest.testmod()