MATLAB: What does this command: “@(x) Function” means in matlab

@anonymous function

function mse_calc = mse_test(x, net, inputs, targets)
   net = setwb(net, x');
   y = net(inputs);
   mse_calc = sum((y-targets).^2)/length(y);
end
inputs = (1:10);
targets = cos(inputs.^2);
n = 2;
net = feedforwardnet(n);
net = configure(net, inputs, targets);
h = @(x) mse_test(x, net, inputs, targets);
ga_opts = gaoptimset('TolFun', 1e-8,'display','iter');
[x_ga_opt, err_ga] = ga(h, 3*n+1, ga_opts);

Best Answer

That's a function handle. See this link:
http://www.mathworks.com/help/matlab/matlab_prog/creating-a-function-handle.html?searchHighlight=function%20handle
The function handle can point to an existing function (e.g., an m-file function), or it can point to an anonymous function (i.e., one created on the fly at the handle creation). E.g.
>> a = 5  % a constant
a =
     5
>> b = 3  % another constant
b =
     3
>> h = @(x) a*x+b  % an anonymous function handle for the linear expression a*x+b
h = 
    @(x)a*x+b
>> h(4)  % evaluate the function handle h for an input of 4
ans =
    23
>> h(7)  % evaluate the function handle h for an input of 7
ans =
    38
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