how to solve Index exceeds the number of array elements (1)?

Hy guys im writing the following code

% creating an array for D %
D_array = 1:1:40;

% preallocation for optimal distance & cost %
Optimal_distance = zeros(1,length(D));
Cost = zeros(1,length(D));

% Newton's Raphson Method %
for j = 1:length(D_array)
D = D_array(j);
    
% Newton-Raphson's Method %
% initial guess %
x0 = 60;
% 1st derivative value %
fx = @(x) (C_S1)*sqrt(D^(2)+x.^(2))+(C_O1)*(L-x);
% 2nd derivative value %
gx = @(x) ((C_S1)*x./sqrt(x.^(2)+D^2))-(C_O1);
g = g(x0);

Precision = 0.01;

while abs(g) > Precision
    % new 1st derivative value %
    f= fx(x0);
    % Newton-Raphson's formula %
    x0 = x0 - f/g;
    % new 2nd derivative value %
    g= gx(x0);
end

Cost(j) = g;
Optimal_distance(j) = x0;
end

Im trying to get values of x0 where my value of D changes but when i run the code i get the following error message;

Index exceeds the number of array elements (1).

Error in Q1c (line 32)

g = g(x0);

How can I solve this problem?

Answer 1

[Jan]

Maybe you mean:

g = gx(x0);
%    ^

[Aaron Fredrick]

oh thanks, what a silly mistake

Now i fixed it but my code is not really finishing its run, could you help me out in this?

[Jan]

I assume abs(g) > Precision is not a matching criterion. I cannot run your code to test this, because there are missing variables, at least C_S1.

[Aaron Fredrick]

% data %
L = 120;
C_S1 = 2.5e+06;
C_O1 = 2e+06;

[Jan]

Use the debugger to check the values: g does not reach a fix point near to 0, but it is iterating between -4499994.58631 and 499560.68281.

[Aaron Fredrick]

How can I modify my code so i can get a proper output?