Get function handle of fit function in matlab and assign fit parameters

Question

I'm fitting custom functions to my data. After obtaining the fit I would like to get something like a function handle of my fit function including the parameters set to the ones found by the fit. I know I can get the model with

formula(fit) 

and I can get the parameters with

coeffvalues(fit) 

but is there any easy way to combine the two in one step?

Answer 1

This little loop will do the trick:

x = (1:100).';  %'
y = 1*x.^5 + 2*x.^4 + 3*x.^3 + 4*x.^2 + 5*x + 6;
fitobject = fit(x,y,'poly5');  

cvalues = coeffvalues(fitobject);
cnames = coeffnames(fitobject);
output = formula(fitobject);

for ii=1:1:numel(cvalues)
    cname = cnames{ii};
    cvalue = num2str(cvalues(ii));
    output = strrep(output, cname , cvalue);
end

output = 1*x^5 + 2*x^4 + 3*x^3 + 4*x^2 + 5*x + 6

The loop needs to be adapted to the number of coefficients of your fit.

Edit: two slight changes in order to fully answer the question.

fhandle = @(x) eval(output)

returns a function handle. Secondly output as given by your procedure doesn't work, as the power operation reads .^ instead of x, which can obviously be replaced by

strrep(output, '^', '.^');