Curve Fitting Using External Function

Using the Curve Fitting Toolbox, is it possible to put the fitting function outside of the fittype? A general example of the way I want this to be is:

FitOpt=fitoptions('Method', 'NonlinearLeastSquares','Lower',0.1*Y00, 'Upper',10*Y00,'StartPoint',Y00); 
XYFit=fittype(MyFitFunction(a,X),'dependent', {'y'}, 'independent' , {'x'},'coefficient', {'E'});
f1 = fit(x0,y0,XYFit,FitOpt)
.
.
.
function F0=MyFitFunction(a,x)
    F0=a*x.^2-1./x);
end

Where I would like MyFitFunction to be outside the fittype definition, but when I try this I get this error message:

Unrecognized function or variable 'a'

If I take the function into the fittype and write:

XYFit=fittype(@(a,X) a*x.^2-1./x),'dependent', {'y'}, 'independent' , {'x'},'coefficient', {'E'});

then it will work, but this is not the form that I want.

How is this possible?

Answer 1

[Image Analyst]

Did you try

XYFit=fittype(@MyFitFunction(a,X),..........................

[Saeid]

If I do that, I get this error message:

File: FitElong.m Line: 8 Column: 33

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

[Image Analyst]

Sorry I don't have that toolbox so I can't try anything. Maybe try

XYFit=fittype(@MyFitFunction,..........................

[Saeid]

Hi,

whenI do that, I see a new error message:

Error using fittype>iCreateFittype (line 362)

First input argument must be a string scalar or character vector, cell array or anonymous function.

Error in fittype (line 330)

obj = iCreateFittype( obj, varargin{:} );

[Image Analyst]

Call tech support because I don't have that function.