MATLAB: Non Linear regression

MATLABnon-linear regression

% name: myfun.m file
function yhat = myfun(beta,X)
b1 = beta(1); %(Feight multiplier)
b2 = beta(2); %(Freight rate multiplier)
e = X(1); %(Economic growth)
p = X(2); %(Previous year freight)
r = X(3); %(Real freight rate change)
yhat = p*(1.0+(e*b1))*(1.0+(r*b2));
inputs are
x=(11,3) Matrix
y= (11,1) Matrix
beta0 = rand(11,2) Matrix
when i run the script i get the following;
   beta = nlinfit(X,y,'myfun',beta0)
  ??? Error using ==> nlinfit at 127
  MODELFUN should return a vector of fitted values the same length as Y.
I dont understand what the error is can someone please help.
Thanks in advance

Best Answer

% name: myfun.m file
function yhat = myfun(beta,X)
b1 = beta(1); %(Freight multiplier)
b2 = beta(2); %(Freight rate multiplier)
e = X(:,1); %(Economic growth)
p = X(:,2); %(Previous year freight)
r = X(:,3); %(Real freight rate change)
yhat = p.*(1.0+(e*b1)).*(1.0+(r*b2));
inputs are
x=(11,3) Matrix
y= (11,1) Matrix
beta0 = rand(11,1) Matrix
Hope this helps
Greg
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