text12.m

fit programme for a serials of data

%input datas
y=[0.898 2.38 3.07 1.84 2.02 1.94 2.22 2.77 4.02 4.76 5.46 6.53 10.9 16.5 22.5 35.7 50.6 61.6 81.8];
n=length(y);
x=1:n;
%turn y=aexp(bx) into ln(y)=ln(a)+bx
y1=log(y);
%solve linear fit
A=polyfitxy(x,y1,1);
a=exp(A(1))
b=A(2)
disp(sprintf('y=%fexp(%fx)',a,b));
f=@(x) a*exp(b*x);
delta=zeros(1,n);
for i=1:n
   delta(i)=y(i)-f(x(i));
end
aversqrt=norm(delta,2)
maxdeviate=norm(delta,inf)
A=fitcurvedemo(x,y)
a=A(1);
b=-A(2);
disp(sprintf('y=%fexp(%fx)',a,b));
f=@(x) a*exp(b*x);
delta=zeros(1,n);
for i=1:n
   delta(i)=y(i)-f(x(i));
end
aversqrt=norm(delta,2)
maxdeviate=norm(delta,inf)