# Source code for simplestatistics.statistics.geometric_mean

"""
Implements geometric_mean() function.
"""

# I need sane division that returns a float not int
from __future__ import division

# Are you trying to use python3?
# if yes, reduce is now in functools
# ref: http://stackoverflow.com/questions/8689184/python-name-reduce-is-not-defined
# instead of using an if statement, I'll just import reduce from functools anyway
from functools import reduce

# geometric mean
#
# a mean function that is more useful for numbers in different
# ranges.
#
# this is the nth root of the input numbers multipled by each other
#
# This runs on O(n), linear time in respect to the array
[docs]def geometric_mean(data):
"""
The geometric mean_ uses the product of a set of numbers to determine their central tendency,
as opposed to the regular arithmetic mean which uses their sum.

.. _geometric mean: https://en.wikipedia.org/wiki/Geometric_mean

Equation:
.. math::
\\sqrt[n]{x_1 x_2 \\dotso x_n}

Args:
data: A list of numeric objects.

Returns:
A float object.

Examples:
>>> geometric_mean([1])
1.0
>>> geometric_mean([1, 10])
3.1622776601683795
"""
return pow(reduce(lambda v, mem: v * mem, data, 1.0), 1 / float(len(data)))