fit_profile_fxdrg

 Fit profile for a monotonous function

 by F-X Duthoit (CEA/DSM/IRFM, francois-xavier.duthoit@cea.fr) and R.Goupillou (CEA/DSM/IRFM, romain.goupillou@cea.fr)

0001 function [y0,ya,ey1,ey2,chi2] = fit_profile_fxdrg(x,y,model,init,dispfit)
0002 %
0003 % Fit profile for a monotonous function
0004 %
0005 % by F-X Duthoit (CEA/DSM/IRFM, francois-xavier.duthoit@cea.fr) and R.Goupillou (CEA/DSM/IRFM, romain.goupillou@cea.fr)
0006 %
0007 if nargin == 2,
0008     model = 1;
0009     init = [2,2];
0010     dispfit = 0;
0011 elseif nargin == 3,
0012     init = [2,2];
0013     dispfit = 0;
0014 elseif nargin == 4,
0015     dispfit = 0;
0016 end
0017 %
0018 y0 = y(1);
0019 ya = y(end);
0020 %
0021 if model == 1,
0022     [z,chi2] = fminsearch(@(z) sum((y - ((y0 - ya)*(1 - x.^z(1)).^z(2) + ya)).^2),init);
0023     ey1 = z(1);
0024     ey2 = z(2);
0025 elseif model == 2,
0026     [z,chi2] = fminsearch(@(z) sum((y - ((y0 - ya)*(exp(z) - exp(z*x.*x))/(exp(z)-1) + ya)).^2),init);
0027     ey1 = z;
0028     ey2 = NaN;
0029 end
0030 %
0031 if dispfit,
0032     if model == 1,
0033         yfit = (y0 - ya)*(1 - x.^ey1).^ey2 + ya;
0034     elseif model == 2,
0035         yfit = (y0 - ya)*(exp(z) - exp(ey1*x.*x))/(exp(ey1)-1) + ya;    
0036     end
0037     figure('Name','Fit profile'),plot(x,y,'r',x,yfit,'b-');legend('Data','Fit')
0038 end
0039 %
0040 
0041