add 2

lu_tridiag.m

@@ -0,0 +1,26 @@
+%e, f, and j should all be vectors
+%A matrix must be square in order to run LU decomposition
+%This function will output:
+    %diagonal of upper matrix
+    %off diagonal of upper matrix
+    %off diagonal of lower matrix
+function [ud,uo,lo]=lu_tridiag(e,f,g);
+ud = zeros(length(f), 1);
+uo = zeros(length(f)-1, 1);
+lo = zeros(length(f)-1, 1);
+
+lo = g;       %off diagonal of lower matrix=off diagnol vectors
+ud(1)=f(1);   %location one of upper diagonal= dignol vector at location 
+uo(1) = g(1); %location one of upper matrix = off diagnol vector
+k = 2;        %Starts off the while loop
+
+while k <= length(f)-1
+    lo(k-1) = e(k-1)/(ud(k-1));
+    uo(k) = g(k);
+    ud(k) = f(k)-(lo(k-1)*uo(k-1));
+    k = k + 1;
+end
+lo(k-1) = e(k-1)/(ud(k-1)); %Need these two equations otherwise the last value wont work
+ ud(k) = f(k)-(lo(k-1)*uo(k-1)); 
+
+