%%Example1 nonlinear data
 %x1=[0	1	2	3	4	5	6	7	8	9];
%y1=[3.8	3.7	4.0	3.9	4.3	4.2	4.2	4.4	4.5	4.9];
x1=-2:2;
y1=[1 2 3 3 4];
plot(x1,y1,'-o')% Plot the data
fun=@(x,x1)x(1)+x(2)*x1+x(3)*x1.^2;
x0=[0.2 0.5 0.02]; % initial guess
times = linspace(x1(1),x1(end));
%[x,resnorm,residual,exitflag,output,lambda,jacobian] = lsqcurvefit(fun,x0,x1,y1)
[x] = lsqcurvefit(fun,x0,x1,y1)
plot(x1,y1,'ko',times,fun(x,times),'b-','LineWidth',2)%  Linear fit curve plot  
legend('Data','nonlinear fit')
title(' Quadratic model curve fit')
xlabel('x')
ylabel('y')
grid on