help me about nlinfit

i want to solve nonlinear regression problem. input variable 'x' is two element. also output variable 'T' = two element.

but An error has occurred in matlab.

how can i solve it.

help me.....

here is my code.

clear all close all clc;

x(1,:) = 0:1:100; x(2,:) = 100:1:200; v = [4 8 5 3 ]; mdl = @(b,t)( b(1)*t.^3 + b(2)*t.^2 + b(3)*t + b(4)); T = mdl(v,x); S = mdl(v,x) + 10000*randn(1,101); beta0 = [0 0 0 0]; beta = nlinfit(x,S,mdl,beta0); %beta %result = mdl(beta,x);

figure(1) grid on hold on

plot(S','ro') %plot(result)6

Answer 1

[Prajit T R]

Hi Kim

The second argument to the nlinfit function only accepts a vector. So it would be better to fit 'x' element-wise. I have modified your code to illustrate the same. I am not sure if this is what you're looking for, but this might help:

x(1,:) = 0:1:100; 
x(2,:) = 100:1:200; 
v = [4 8 5 3 ]; 
mdl = @(b,t)( b(1)*t.^3 + b(2)*t.^2 + b(3)*t + b(4));
T = mdl(v,x); 
S = mdl(v,x) + 10000*randn(1,101);
beta0 = [0 0 0 0]; 
size(x)
size(S)
beta1 = nlinfit(x(1,:),S(1,:),mdl,beta0); 
beta2 = nlinfit(x(2,:),S(2,:),mdl,beta0);
result = mdl([beta1 beta2],x);
figure(1) 
grid on 
hold on
plot(S','ro') 
figure
plot(result)

Cheers