i have problem using feval function

>> x(1:7) = randi([4,50],1,7);
d(1:7) = randi([3,5],1,7);
for i = 1 : 7
    sum = 0;
w = 1;
sum = sum + w*(x(i) - d(i));
end
f(1) = sum;

for i = 1 : 7
 sum = 0;
    sum = sum + w*(x(i) - 4);
end
f(2) = sum;

f = f(1) + f(2);
>> a = Particle_Swarm_Optimization (10,2,[4 50;3 5],f,randi(100,50),2,2,2,0.4,0.9,3);
Completed  0  % ...Error using feval
Argument must contain a string or function_handle.

Error in Particle_Swarm_Optimization (line 103)
        availability(p,itr)=feval(Food_availability,parameter);

Answer 1

[Geoff Hayes]

Arudrha - according to the documentation for the PSO at the FEX Particle Swarm Optimization, the fourth input parameter must be a function of one variable. Pramit Biswas' example is of a function that accepts an array input as

 function f = funfunc(array)
    a=array(1);
    b=array(2);
    f = a+b ;
 end

In your code, you are not passing a handle to a function but are instead passing the scalar value f.