spectral centroid calculation

spectral_centroid.py

# http://en.wikipedia.org/wiki/Spectral_centroid

from __future__ import division
from numpy import abs, sum, linspace
from numpy.fft import rfft

spectrum = abs(rfft(signal))
normalized_spectrum = spectrum / sum(spectrum)  # like a probability mass function
normalized_frequencies = linspace(0, 1, len(spectrum))
spectral_centroid = sum(normalized_frequencies * normalized_spectrum)

# Spectral centroid is calculated as a ratio.  Multiply by your maximum frequency bin to get real frequency.