Simple lsqcurvefit does not work properly
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Hello. I would like to do a simple lsqcurvefit. But it seems to be that I cannot write the code properly. The data is attached. For some background.
My code is:
n = 400; % number of partitions
l = 13; % length of Basilarmembran in cm
x = linspace(0.01, 13, n)'; % length of each partition 0.01 - 13 cm
b = 0.5; % width in cm at Helicotrema
t = 0.04; % height in cm
beff = b.*x/l; % length of each trapezium
dx = x(2:n) - x(1:n-1); % length of each mass oszillator
zs = dx.*(beff(1:n-1)+2.*beff(2:n))./(3*beff(1:n-1)+3.*beff(2:n)); % centroid of an trapezial-area
xeff = zs + x(1:n-1); % effectiv distance of each centroid
% ________BASIS The tip counts from x = 0.01 cm (basis) to x = 13 cm (apex)
% | .
% | /|\
% h| /_|_\
% | /__|__\ <-- This is one trapezium
% | / | \
% |___/____|____\
% |_________| APEX
filename = 'stifness.xls';
A = xlsread(filename);
xdata=A(:,1)/10; % x-values in cm
fdata=A(:,2); % y-values in Hz
s0 = [90, 1.7, 0.88]; % inital values, processed by hand
ub = [2e2, 2e0, 1e1]; % upper bound
lb = [1e1, 1e0, 1e-1]; % lower bound
options = optimset('TolFun',1.0e-15,'TolX',1.0e-15);
Gfun = @(s,x) s0(1).*(10.^(s0(2).*(13-x)/13)-s0(3));
fitfun = lsqcurvefit(Gfun,s0,xdata,fdata,lb,ub,options);
Gfuntest1 = s0(1).*(10.^(s0(2).*(13-xeff)/13)-s0(3)); % plot with inital values
Gfuntest2 = fitfun(1).*(10.^(fitfun(2).*(13-xeff)/13)-fitfun(3)); % plot with fitted values
semilogy(xeff, Gfuntest1,'g',xeff,Gfuntest2,'--k',xdata,fdata,'ob'); % plot data
Any suggestion for my little problem? I don't know, why the lsqcurvefit does not change the inital values. They are staying the same. It cannot be that I guessed perfect initial values.
Best regards
Henrik
EDIT: Sorry for the missed data. Now it is attached.
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