function exm051022_1()
%exm051022_1.m   	利用fminsearch指令進行非線性參數估計
k_noise=0.3;
[x,y,STDY]=xydata(k_noise);
a0=[1 1 1 1];
options.TolX=0.01;
options.Display='off';
a=fminsearch('twoexps',a0,options,x,y);
chi_est=twoexps(a,x,y)/STDY^2;
freedom=length(x)-length(a0);
Q=1-chi2cdf(chi_est,freedom);
y_est=a(1)*exp(-a(3)*x)+a(2)*exp(-a(4)*x);
ych='y_e_s_t=';
a1=num2str(a(1));a2=num2str(a(2));a3=num2str(a(3));a4=num2str(a(4));
char_y_est=[ych,a1,'*exp(-',a3,'*x) + ',a2,'*exp(-',a4,'*x)'];
shg,plot(x,y,'b+');hold on,plot(x,y_est,'r');hold off,axis([0,4,0,16])
text(0.4,14,'y=3*exp(-0.4*x)+12*exp(-3.2*x)')
text(0.4,12,char_y_est),text(2.5,9,['chi2=' , num2str(chi_est)])
text(2.5,7,['freedom=' , num2str(freedom)])
text(2.5,5,['Q=' , num2str(Q)])