Scripted general fitting data: Error in fminsearch

I am very new in Matlab. And I am still going through the text book.

And here is a piece of code I tried to fit the exist data.fil. It is a 5*2 data.

      %loading data
      load data.fil; x=data (: ,1 ); y = data (: ,2);

      %plotting
      xmin = min(x); xmax = max(x); npts = 1001;
      dx = (xmax - xmin) / (npts -1); xplot = xmin:dx:xmax;

      %set ifit to 0 and don't continue on to the fit until the user sets it to 1
      ifit = 0;
      while (ifit == 0)
            disp ('Enter an initial guess for the function')
            a = input ('parameters [a1, a2,...] in vector form [...]-');

            %plot data and the initial function guess
            yplot = funcfit (a, xplot);
            plot (x,y, 'b*', xplot, yplot, 'r-');
            xlabel ('x');
            ylabel ('y');
            title ('Initial Guess and Data')
            ifit = input ('0: guess again; 1: fit with this guess - ');
      end

      % Define the option TolX set; look for the best parameters to minimize the leastsq.m function
      option = optimset ('TolX', 1e-4);
      a = fminsearch (@leastsq, a, option, x, y); 

      % evaluate the function with the final fit parameters
      yplot = funcfit (a, xplot);

      % plot
      plot (x,y, 'b*', xplot, yplot, 'r-');
      xlabel ('x')
      ylabel ('y')
      title ('Final fit and data')

And here are the functions being called: funcfit.m

    % fitting function, find a1, a2 to fit the fuction f represents
    function f = funcfit(a,x)
    f= a(1).*exp(a(2).*x);

leastsq.m

%the square of minimum between the y in the data:fil and fiting 
function s=leastsq(a,x,y)
s = sum ((y - funcfit (a,x).^2);

So when I run the script, I got

Enter an initial guess for the function
parameters [a1, a2,...] in vector form [...]-

I tried [1,1], and it fits.

0: guess again; 1: fit with this guess -

So I input 1. The it shows below:

Attempt to execute SCRIPT fminsearch as a function:
M:\pc\Desktop\Matlab start\fminsearchfitting\fminsearch.m

Error in fminsearch (line 51)
a = fminsearch (@leastsq, a, option, x, y);

I have checked many times, and I do not know where it is wrong. I learnt fminsearch only process scalar. How do I do?

Many thanks.

Answer 1

[Star Strider]

You may have named your script file (or some other script in your user directory) as ‘fminsearch’.

Type this line in the Command Window:

which fminsearch -all

On my computer (Windows 8 64), I get one result:

C:\Program Files\MATLAB\R2014a\toolbox\matlab\optimfun\fminsearch.m

If you get more than that, especially if one is your script file, rename your script file.

[Xin]

Thanks. I got only one fminsearch.m. But I still changed the name for script. It still shows so.

[Star Strider]

I see the problem.

Change:

a = fminsearch (@leastsq, a, option, x, y);

to:

a = fminsearch (@(a) @leastsq(a, x, y), a);

I didn’t run your code so I don’t know if that’s the only problem, but it should at least not throw the error now.