Simple Spectral Centroid Algorithm

#define PI 3.14159265359

/*
    Compute the spectral centroid in hertz for an input signal of finite length.
        This is a very simplistic implementation which can be improved upon.

        input        -- the input signal buffer.
        sample_count -- the size of the input signal buffer.
        sample_rate  -- the sampling rate in hertz.
*/

double spectral_centroid(const double *input, int sample_count, double sample_rate)
{
    double aPowerSum = 0.0, bPowerSum = 0.0;

    for (int i = 1; i < sample_count; ++i)
    {
        double a = input[i], b = input[i] - input[i-1];
        aPowerSum += a*a;
        bPowerSum += b*b;
    }

    return sqrt(bPowerSum / aPowerSum) * sample_rate / (2.0*PI);
}

//To the extent possible under law, Evan D. Balster has waived all copyright and related or neighboring rights to this Spectral Centroid Algorithm.  See: https://creativecommons.org/publicdomain/zero/1.0/

//This code was updated on 2016-02-09 to correct several math errors pointed out by Oriol Romani Picas.