% Example 14.1c (Physics 330)

%*********************************************************
% Uses fminsearch to least squares fit
% a function defined in funcfit.m to
% data read in from data.fil
%*********************************************************

clear;close

% read the data file and load x and y

load data.fil;
x=data(:,1);
y=data(:,2);

% set up for the plot of the fitting function

xmin=min(x);
xmax=max(x);
npts=1001;
dx=(xmax-xmin)/(npts-1);
xplot=xmin:dx:xmax;

% set ifit to 0 and don't continue on to the fit until
% the user sets it to 1

ifit=0;

while ifit==0

disp(' Enter an initial guess for the function ')
a=input('parameters [a1,a2,...] in vector form [...]- ')

% plot the data and the initial function guess

yplot=funcfit(a,xplot);

plot(x,y,'b*',xplot,yplot,'r-')
xlabel('x')
ylabel('y')
title('Initial Guess and Data')

ifit=input(' Enter 0 to guess again, 1 to try to fit with this guess - ')

end

%*********************************************************
% Do the fit with the option TolX set; fminsearch will adjust a
% until each of its elements is determined to within TolX.
% If you think fminsearch could do better than it did, reduce TolX.
%*********************************************************

option=optimset('TolX',1e-5);
a=fminsearch(@leastsq,a,option,x,y)

% plot the data and the final function fit

yplot=funcfit(a,xplot);

% Plot the final fit and the data

plot(x,y,'b*',xplot,yplot,'r-')
xlabel('x')
ylabel('y')
title('Final Fit and Data')