How can I fix this problem?

I'm trying to run my script, but I do not get my result. It seems to my Matlab does not execute my code. How can I fix this problem?

function x=LUNEW(A,b)
%First of all, I will combine the matrix A with the matrix b in this way
%[A|b]
% Gauss Elimination
Ab = [A,b];
n = length(A);
% the size of matrix A.
%L=eye(n);
%[A,b]=pivot_element(A,b);
%back substitution
x=zeros(n,1);
%  for i=10:-1:1
%      x(i)=(Ab(i,end)-Ab(i,i+1:n)*x(i+1:n))/Ab(i,i);
%  end
end
%A(1,1) as pivot element
function [A,b]=pivot_element(A,b)
for i=2:n
  alpha= Ab(i,1)/Ab(1,1);
  L(i,1)=alpha;
  Ab(i,:)= Ab(i,:)- alpha*Ab(1,:);  % it is like (R2=R2-
  alpha*R1)replacement.
end
% % A(2,2) as piovt element
for i=3:n
  alpha= Ab(i,2)/Ab(2,2);
  L(i,2)=alpha;
  Ab(i,:)= Ab(i,:)- alpha*Ab(2,:);  %interchange the rows
end
% % A(3,3) as piovt element
for i=4:n
  alpha= Ab(i,3)/Ab(3,3);
  L(i,3)=alpha;
  Ab(i,:)= Ab(i,:)- alpha*Ab(3,:);
end
% % A(4,4) as piovt element
for a=5:n
  alpha= Ab(a,4)/Ab(4,4);
  L(a,4)=alpha;
  Ab(a,:)= Ab(a,:)- alpha*Ab(4,:);
end
% % A(5,5) as piovt element
for d=6:n
  alpha= Ab(d,5)/Ab(5,5);
  L(d,5)=alpha;
  Ab(d,:)= Ab(d,:)- alpha*Ab(5,:);
end
% % A(6,6) as piovt element
for f=7:n
  alpha= Ab(f,6)/Ab(6,6);
  L(f,6)=alpha;
  Ab(f,:)= Ab(f,:)- alpha*Ab(6,:);
end
% % A(7,7) as piovt element
for h=8:n
  alpha= Ab(h,7)/Ab(7,7);
  L(h,7)=alpha;
  Ab(h,:)= Ab(h,:)- alpha*Ab(7,:);
end
% % A(8,8) as piovt element
for j=9:n
  alpha= Ab(j,8)/Ab(8,8);
  L(j,8)=alpha;
  Ab(j,:)= Ab(j,:)- alpha*Ab(8,:);
end
% % A(9,9) as piovt elements
for k=10:n
  alpha= Ab(k,9)/Ab(9,9);
  Ab(k,:)= Ab(k,:)- alpha*Ab(9,:);
  L(k,9)=alpha;
end
% % A(9,9) as piovt element
% for k=9;
%     alpha= Ab(k,9)/Ab(9,9);
%     Ab(k,:)= Ab(k,:)- alpha*Ab(9,:);
%     L(k,9)=alpha;
% end
%U=Ab(1:n,1:n);
%
%L*U;
%%%%%%%%%%%%%%%%%%%%
%back substitution
x=zeros(n,1);
for i=10:-1:1
  x(i)=(Ab(i,end)-Ab(i,i+1:n)*x(i+1:n))/Ab(i,i);
end
%
%%%%%%%%%%%%%%%%%%%%
%compare with backslash
%A\b;
end

[Image Analyst]

What did you supply for A and b in

x = LUNEW(A, b);

when you called it? You DID supply arguments, didn't you? You didn't just hit the green run triangle did you?

http://www.mathworks.com/matlabcentral/answers/13205#answer_18099

[fs]

I did provide input for my A,b.

[Stephen23]

It works for me:

 >> LUNEW(1,2)
 ans =
     0

[Guillaume]

As it is the main function (there's no script in the code you've presented) only does one useful thing: create a zero row vector the same length as the largest dimension of the input A. That is all.

Now if some of the lines were to be uncommented, it could do a lot more but don't expect us to guess which lines that should be.

Answer 1

[Jan]

The code, which is executed is:

function x = LUNEW(A, b)
Ab = [A,b];
n  = length(A);
x  = zeros(n,1);
end

As Guillaume has mentioned already, all other lines are not executed, because they are commented.

You can check this by using the debugger: https://www.mathworks.com/help/matlab/debugging-code.html. Set a breakpoint in the first line of code (the red dots on the left side in the editor) and step through the code line by line. Then it gets clear, where what is done.