lu_tridiag.m

function [ud,uo,lo]=lu_tridiag(e,f,g)
%Takes main diaganol and diaganol to the top and bottom and make matrix A
%and then an Identity matrix B is made.
%The matrix A is then turned into the upper matrix while B turns into the
%lower matrix in LU decomposition.
%The function outputs the main diagnol of the upper matrix and the off
%diagnol of the lower and upper matrices.
A=diag(e,-1)+ diag(f)+diag(g,1);
B=eye(length(f));
for i=1:length(e)
x=A(i+1,i)/A(i,i);

A(i+1,i)= (-e(i)/f(i))*f(i)+e(i);

A(i+1,i+1)= (-x)*g(i)+f(i+1);


B(i+1,i)=x;


ud(1)=A(1,1);
ud(i+1)= A(i+1,i+1);
uo(i)=A(i,i+1);
lo(i)=B(i+1,i);
end

end