backward_col.m

various matlab programs to slove various problems

function [b]=backward_col(U,b)
[n]=mat_square(U);
l = min(diag(abs(U))); 
if l == 0
  disp('Error: the matrix is singular'); b = [];
  break
end
for j = n:-1:2, 
   b(j)=b(j)/U(j,j); 
   b(1:j-1)=b(1:j-1)-b(j)*U(1:j-1,j); 
end; 
b(1) = b(1)/U(1,1);
return