Python/maths/gaussian.py

"""
Reference: https://en.wikipedia.org/wiki/Gaussian_function

python/black : True
python : 3.7.3

"""
from numpy import pi, sqrt, exp



def gaussian(x, mu: float = 0.0, sigma: float = 1.0) -> int:
    """
    >>> gaussian(1)
    0.24197072451914337
      
    >>> gaussian(24)
    3.342714441794458e-126

    Supports NumPy Arrays
    Use numpy.meshgrid with this to generate gaussian blur on images.
    >>> import numpy as np
    >>> x = np.arange(15)
    >>> gaussian(x)
    array([3.98942280e-01, 2.41970725e-01, 5.39909665e-02, 4.43184841e-03,
           1.33830226e-04, 1.48671951e-06, 6.07588285e-09, 9.13472041e-12,
           5.05227108e-15, 1.02797736e-18, 7.69459863e-23, 2.11881925e-27,
           2.14638374e-32, 7.99882776e-38, 1.09660656e-43])
           
    >>> gaussian(15)
    5.530709549844416e-50

    >>> gaussian([1,2, 'string'])
    Traceback (most recent call last):
        ...
    TypeError: unsupported operand type(s) for -: 'list' and 'float'

    >>> gaussian('hello world')
    Traceback (most recent call last):
        ...
    TypeError: unsupported operand type(s) for -: 'str' and 'float'

    >>> gaussian(10**234) # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
        ...
    OverflowError: (34, 'Result too large')

    >>> gaussian(10**-326)
    0.3989422804014327

    >>> gaussian(2523, mu=234234, sigma=3425)
    0.0
  """
    return 1 / sqrt(2 * pi * sigma ** 2) * exp(-(x - mu) ** 2 / 2 * sigma ** 2)


if __name__ == "__main__":
    import doctest

    doctest.testmod()