diff --git a/maths/geometric_mean.py b/maths/geometric_mean.py new file mode 100644 index 000000000..240d519ad --- /dev/null +++ b/maths/geometric_mean.py @@ -0,0 +1,55 @@ +""" +The Geometric Mean of n numbers is defined as the n-th root of the product +of those numbers. It is used to measure the central tendency of the numbers. +https://en.wikipedia.org/wiki/Geometric_mean +""" + + +def compute_geometric_mean(*args: int) -> float: + """ + Return the geometric mean of the argument numbers. + >>> compute_geometric_mean(2,8) + 4.0 + >>> compute_geometric_mean('a', 4) + Traceback (most recent call last): + ... + TypeError: Not a Number + >>> compute_geometric_mean(5, 125) + 25.0 + >>> compute_geometric_mean(1, 0) + 0.0 + >>> compute_geometric_mean(1, 5, 25, 5) + 5.0 + >>> compute_geometric_mean(2, -2) + Traceback (most recent call last): + ... + ArithmeticError: Cannot Compute Geometric Mean for these numbers. + >>> compute_geometric_mean(-5, 25, 1) + -5.0 + """ + product = 1 + for number in args: + if not isinstance(number, int) and not isinstance(number, float): + raise TypeError("Not a Number") + product *= number + # Cannot calculate the even root for negative product. + # Frequently they are restricted to being positive. + if product < 0 and len(args) % 2 == 0: + raise ArithmeticError("Cannot Compute Geometric Mean for these numbers.") + mean = abs(product) ** (1 / len(args)) + # Since python calculates complex roots for negative products with odd roots. + if product < 0: + mean = -mean + # Since it does floating point arithmetic, it gives 64**(1/3) as 3.99999996 + possible_mean = float(round(mean)) + # To check if the rounded number is actually the mean. + if possible_mean ** len(args) == product: + mean = possible_mean + return mean + + +if __name__ == "__main__": + from doctest import testmod + + testmod(name="compute_geometric_mean") + print(compute_geometric_mean(-3, -27))