ipeidg0.m

various matlab programs to slove various problems

function [u,x]=ipeidg0(I,n,a,u0,bc)
nx = n(1); 
h = (I(2)-I(1))/nx; 
x = [I(1)+h/2:h:I(2)]; 
t = I(3); 
u = (eval(u0))';
nt = n(2); 
k = (I(4)-I(3))/nt;
lambda = k/h; 
e = ones(nx,1);
A=spdiags([-a*lambda*e, (1+a*lambda)*e],-1:0,nx,nx);
[L,U]=lu(A);
for t = I(3)+k:k:I(4)
   f = u;
   if a > 0
      f(1) = a*bc(1)+f(1);
   elseif a <= 0
      f(nx) = a*bc(2)+f(nx);
   end
   y = L \ f; 
   u = U \ y;
end
return