what does this command: "@(x) Function" means in matlab?

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Saeed
Saeed 2016-9-13
编辑： mohd El Tahir 2021-3-29
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);
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James Carter
James Carter 2019-7-18
编辑：James Carter 2019-7-18
I am not an expert, but I think I know what's going on here. The @fun (handle AKA pointer) declaration appears to be designed to work on a function of one argument or variable, in the form of fun(x). If you have a routine that takes multiple arguments such as fun(x, y, z), then the pointer construct breaks down as the functions that would call at @fun, such as fzero,have no way of filling in the other arguments.
So the declaration construct of '@(x) fun(x,y,z)' tells Matlab that the variable x is the one to work upon. Note that the y and z need to be defined within the scope of the routine calling this constuct. The example code that you posted shows that 'net' 'inputs' and 'target' are all defined in the scope of the
h = @(x) mse_test(x, net, inputs, targets);
statemet. The variable 'x' is defined in the @(x) declaration syntax.
Anyway this worked for me with
>> test = MScanWvlMap(22500, pMSTarbDnSmth);
>> findFun = @(x) MScanWvlMap(x, pMSTarbDnSmth, test);
>> atest = fzero(findFun,27000)
atest =
2.249999999999971e+04

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James Tursa
James Tursa 2016-9-13
编辑：James Tursa 2016-9-13
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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