%--------------------------------------------------------------------------
%      Sigmo_fit is function developped by J.C. COMTE  comtejc@gmail.com
%                              CNC  UMR CNRS 5229.
%                          Last Release  July. 2007
%         This work is protected by the CeCILL-C Licence (see below).
%
%
%  x and y are two unidimensional vector.
%  
%  
%  a is the coefficient of the sigmoide y=tanh(a*(x-xo));
%  X and Y returns the data fitting.
%
%
%  
% This software is governed by the [CeCILL|CeCILL-B|CeCILL-C] license under
%French law and
% abiding by the rules of distribution of free software.  You can  use, 
% modify and/ or redistribute the software under the terms of the 
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% "http://www.cecill.info". 
% 
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% modify and redistribute granted by the license, users are provided only
% with a limited warranty  and the software's author,  the holder of the
% economic rights,  and the successive licensors  have only  limited
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% software by the user in light of its specific status of free software,
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%--------------------------------------------------------------------------

function [a xo x Y]=sigmo_fit(x,y)

t=x;

Moy=(min(y)+max(y))/2;
y=y-Moy;
l=size(y,2);

M=abs((mean(y(1,1:int32(0.1*l)))-mean(y(1,int32(0.9*l):l)))/2);
N=max([abs(max(y)) abs(min(y))]);
y=y/N;

z=diff(y);
z=convol(z,hamming(5)');
maxi=max(z);
mini=min(z);


if (abs(mini)>abs(maxi))
   maxi=mini;
end;

n=find(z==maxi);
e=int32(n/10);
y=y(n-e:n+e);
y=atanh(y);
x=x(n-e:n+e);

ind = find(isinf(y));
x(ind) = [];
y(ind) = [];

[a b]=Lin_Reg(x,y)

xo=b/a;

Y=Moy+M*tanh(a*(t+xo));
x=t;
plot(t,Y,'r');