Implementation of grid search for a function

I am trying to run a grid search and find x*. but it gives me "Not enough input arguments".

funktion = @(x) sqrt(x) + 2*sqrt(1-x);

x = [0:0.001:1];

x_star_grid = grid(funktion, x)

function [f_benchmark, domain_max] = grid(funktion, domains)

domain_max = -1e+5;

for i = 1:length(domains)

z= domains(i);

disp(z)

f = feval(funktion, z);

if f>=f_benchmark

f_benchmark = f;

domain_max = domains(i);

end

end

end

Answer 1

[Deepak]

Hi @Sardor Butunboev,

To my understanding, you have written a “grid” function in MATLAB to find maximum value of a given function within a specified domain. However, on calling the function the compiler throws the following error: “Not enough input arguments”.

On investigating the code, I found that the error occurs due to incorrect number of output arguments on “grid” function call. The output arguments while calling the function should match the function definition.

Please find below the correct function call to “grid”:

[x_star_grid, f_benchmark] = grid(funktion, x);

Additionally, the variable “f_benchmark” should be initialized with some default value, before using it inside the “if” statement to avoid the “unrecognized variable” error.

f_benchmark = -Inf;  % Initialize f_benchmark to a very low value 

Below is the complete MATLAB code with all the required changes:

funktion = @(x) sqrt(x) + 2*sqrt(1-x); 
x = 0:0.001:1; 
[x_star_grid, f_benchmark] = grid(funktion, x); 

function [f_benchmark, domain_max] = grid(funktion, domains) 
    domain_max = -1e+5; 
    f_benchmark = -Inf;  % Initialize f_benchmark to a very low value 

    for i = 1:length(domains) 
        z = domains(i);     
        f = feval(funktion, z); 
        
        if f >= f_benchmark 
            f_benchmark = f; 
            domain_max = domains(i); 
        end 
    end 
end 

Attaching the documentation of “functions” in MATLAB for reference:

www.mathworks.com/help/matlab/ref/function.html

I hope this resolves the issue.