How should I store the value of f(x) in the output of fsolve?

I saw the example in the fsolve page:

F = @(x) [2*x(1) - x(2) - exp(-x(1));
         -x(1) + 2*x(2) - exp(-x(2))];
x0 = [-5;-5];
options = optimoptions('fsolve','Display','iter');
[x,fval] = fsolve(F,x0,options)

which gives the result:

                                         Norm of      First-order   Trust-region
 Iteration  Func-count     f(x)          step         optimality    radius
     0          3         47071.2                      2.29e+04               1
     1          6         12003.4              1       5.75e+03               1
     2          9         3147.02              1       1.47e+03               1
     3         12         854.452              1            388               1
     4         15         239.527              1            107               1
     5         18         67.0412              1           30.8               1
     6         21         16.7042              1           9.05               1
     7         24         2.42788              1           2.26               1
     8         27        0.032658       0.759511          0.206             2.5
     9         30     7.03149e-06       0.111927        0.00294             2.5
    10         33     3.29525e-13     0.00169132       6.36e-07             2.5

Now, I want to store the last value of f(x), 3.29525e-13, in a file, what should I do?

Answer 1

[Matt J]

>> norm(fval).^2

ans =

   3.2953e-13

[Dan Zhu]

Thank you, didn't expect it to be that simple.