hi am working on a code for gaussian elimination

hi am working on a code for gaussian elimination but I can't get the code to run for non square matrix please what should I do Here is the code and thanks in advance

function [x,U] = gausselim(A,b)
% function to perform gauss eliminination
%FORWARD ELIMINATION
n=length(b);
m=zeros(n,1);
x=zeros(n,1);
for k =1:n-1;
    %compute the kth column of M
    m(k+1:n) = A(k+1:n,k)/A(k,k);
    %compute An=Mn*An-1, bn=Mn*bn-1
    for i=k+1:n;
        A(i, k+1:n) = A(i,k+1:n)-m(i)*A(k,k+1:n);
    end;
    b(k+1:n)=b(k+1:n)-b(k)*m(k+1:n);
end;
U= triu(A);

%BACKWARD ELIMINATION
x(n)=b(n)/A(n,n);
for k =n-1:-1:1;
    b(1:k)=b(1:k)-x(k+1)* U(1:k,k+1);
    x(k)=b(k)/U(k,k);
end;
end

[John D'Errico]

I fixed it for you, but you need to learn how to flag a block of code as such. Otherwise, it is unreadable.

Answer 1

[George Papazafeiropoulos]

The correct function is:

function [x,U]=gausselim(A,b)

% function to perform gauss eliminination

%FORWARD ELIMINATION

n=length(b);

m=zeros(n,1);

x=zeros(n,1);

for k =1:n-1;

      %compute the kth column of M

      m(k+1:n) = A(k+1:n,k)/A(k,k);

      %compute

      %An=Mn*An-1;

      %bn=Mn*bn-1;

      for i=k+1:n

          A(i, k+1:n) = A(i,k+1:n)-m(i)*A(k,k+1:n);

      end;

      b(k+1:n)=b(k+1:n)-b(k)*m(k+1:n);

end

U= triu(A);

%BACKWARD ELIMINATION

x(n)=b(n)/A(n,n);

for k =n-1:-1:1;

      b(1:k)=b(1:k)-x(k+1)* U(1:k,k+1);

      x(k)=b(k)/U(k,k);

end

end

After this try to run the code:

A=rand(5,4);

b=rand(4,1);

[x,U] = gausselim(A,b)

Is this what you want? I hope this helps...

George

[Ifechukwu]

Thanks a lot it helps

Answer 2

[Cory Cress]

I think the command you are looking for is rref :

R = rref(A)

[R,jb] = rref(A)

[R,jb] = rref(A,tol)

It produces a matrix in reduced row echelon form. Perhaps your exercise was to write it yourself, but for others that want to use a built-in function use rref.