ITE / code / H_I_D / base_estimators / HShannon_spacing_Vplin_estimation.m

function [H] = HShannon_spacing_Vplin_estimation(Y,co)
%Estimates the Shannon entropy (H) of Y (Y(:,t) is the t^th sample) using Vasicek's spacing method with piecewise linear correction. Cost parameters are provided in the cost object co.
%
%We make use of the naming convention 'H<name>_estimation', to ease embedding new entropy estimation methods.
%
%REFERENCE: Nader Ebrahimi, Kurt Pflughoeft and Ehsan S. Soofi. Two measures of sample entropy. Statistics and Probability Letters, 20(3):225-234, 1994.
%
%Copyright (C) 2012 Zoltan Szabo ("http://nipg.inf.elte.hu/szzoli", "szzoli (at) cs (dot) elte (dot) hu")
%
%This file is part of the ITE (Information Theoretical Estimators) Matlab/Octave toolbox.
%
%ITE is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
%the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
%
%This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
%MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
%
%You should have received a copy of the GNU General Public License along with ITE. If not, see <http://www.gnu.org/licenses/>.

[d,num_of_samples] = size(Y);

%verification:
    if d~=1
        error('The samples must be one-dimensional for this estimator.');
    end

m = floor(sqrt(num_of_samples));%m/num_of_samples->0, m,num_of_samples->infty; m<num_of_samples/2
Y_sorted = sort(Y);
Y_sorted = [repmat(Y_sorted(1),1,m),Y_sorted,repmat(Y_sorted(end),1,m)];
diffs = Y_sorted(2*m+1:num_of_samples+2*m) - Y_sorted(1:num_of_samples);
c = [1+([1:m]-1)/m,2*ones(1,num_of_samples-2*m),1+(num_of_samples-[num_of_samples-m+1:num_of_samples])/m]; %piecewise linear correction
H = mean(log (num_of_samples / m * diffs./c));


  
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