rayleighmode.m

%-------------------------------------------------------------------------
% RAYLEIGHMODE
%
% Computes mode of a vector/matrix of data that is assumed to come from a
% Rayleigh distribution.
%
% Usage:  rmode = rayleighmode(data, nbins)
%
% Arguments:  data  - data assumed to come from a Rayleigh distribution
%             nbins - Optional number of bins to use when forming histogram
%                     of the data to determine the mode.
%
% Mode is computed by forming a histogram of the data over 50 bins and then
% finding the maximum value in the histogram.  Mean and standard deviation
% can then be calculated from the mode as they are related by fixed
% constants.
%
% mean = mode * sqrt(pi/2)
% std dev = mode * sqrt((4-pi)/2)
% 
% See
% http://mathworld.wolfram.com/RayleighDistribution.html
% http://en.wikipedia.org/wiki/Rayleigh_distribution
%

function rmode = rayleighmode(data, nbins)
    
    if nargin == 1
        nbins = 50;  % Default number of histogram bins to use
    end

    mx = max(data(:));
    edges = 0:mx/nbins:mx;
    n = histc(data(:),edges); 
    [dum,ind] = max(n); % Find maximum and index of maximum in histogram 

    rmode = (edges(ind)+edges(ind+1))/2;
end