Not enough input arguments

Could somebody please explain what this error is and how to fix it.

(Error in goldenmax721 (line 5) xmax_old=max(f(xl),f(xu));

Code:

function[xmax,fval]=goldenmax(f,ea,xl,xu)
phi=0.5*(1+sqrt(5));
tol=1;
iter=0;
xmax_old=max(f(xl),f(xu));
while tol>ea
    iter=iter+1;
    d=(phi-1)*(xu-xl);
    x1=xl+d;
    x2=xu-d;
    if f(x1)>f(x2)
        xl=x2;
        x2=x1;
        d=(phi-1)*(xu-xl);
        x1=xl+d;
        xmax=x1;
        fval=f(x1);
    else
        xu=x1;
        x1=x2;
        d=(phi-1)*(xu-xl);
        x2=xu-d;
        xmax=x2;
        fval=f(x2);
    end
    tol=abs((xmax-xmax_old))*100;
    xmax_old=xmax;
end
end

Answer 1

[Walter Roberson]

You cannot run that code by simply pressing the green Run button to run it. You must go down to the command line and invoke the function passing in four arguments, the first of which is a function handle and the other three of which are numeric. (Or you could write a bit of code that made the call instead of doing it at the command line.)

Answer 2

[KSSV]

YOu have to define/ give values of f,ea,xl,xu to the function. I think you are running the function directly.

f = your value ;   % enter your value 
ea = your value ; 
xl = your value ; 
xu = yourvalue ; 
[xmax,fval]=goldenmax(f,ea,xl,xu)