how to save past outputs of a function

I have the following code :

    function  NM
    options = optimset('Display','iter','TolX',1e-10,'TolFun',1e-10);
    [x,fval] = fminsearch(@(x)ban2(x),1,options);

    function ban1 = ban2(x)
    x1 = x
    iono_layer_parms = [x(1), x(2), -1, -1, -1, -1]; 
    [iono, iono_extra] = iri2012(lat, lon, x, UT,ht_start, ht_step,num_hts); 
    ionofreq = 0.008978663597663*sqrt((10.^(-6))*(iono(1,18:end))); 
    D6xb = interp1(alt3(101:697),D6xa(101:697),alt(26:175));
    D6xc = 0.008978663597663*sqrt(D6xb);
    ban = ionofreq(9:158) - D6xc;
    ban1 = sum(ban.^2)

I want to save the variables x used in each iteration. I tried using persistent variables at the fourth line of the code but got error message :The PERSISTENT declaration must precede any use of the variable. x.

I also tried to use persistent variables at other places in function ban1 but got the same error message. Any help will be greatly appreciated.

Answer 1

[dpb]

Use the output function option to write the function to return the values. There's an example in the documentation that creates a history as you're looking for...

http://www.mathworks.com/help/optim/ug/optimization-options-reference.html#f11022

In the local doc for R2012b here there's an example w/ a history specifically like you're asking; that doesn't seem to show up so easily anyway w/ the online doc's...not sure what's changed if anything besides the documentation.

[Dev]

Thank You very much. It worked.