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function [L,U,y,x]=LU(A,B)
8 S3 E9 e8 f6 M' T+ M: }1 Sn=length(A);
3 e" A' ?6 ], e. I2 g# w# W. T# oL=eye(n);. J3 j- t. I! Q
U=zeros(n,n);* V% c1 V9 E# m& A8 d+ L1 G
for k=1:n 6 G) o0 `: u) k. M& G7 y& t
for j=k:n6 I6 J) U3 U, J
c=0;
% o) C/ B+ v1 Z5 a4 K for i=1:k-1, t6 P( M" h p, z+ {
c=c+L(k,i)*U(i,j);
9 u' [; e0 `: U Y9 X# K$ H end
1 Q8 B D8 {* n9 R U(k,j)=A(k,j)-c;. P( |' v' _0 _6 }# Q: Q2 a) S
end) D9 A7 n o: \( @. k7 e- m5 {: T
if U(k,k)==0: z' m6 R1 n) V W( E0 c/ B
for i=k+1:n: q0 N) t* j& s# o K, K% s+ Q/ k
z=i;
: r0 I. `3 ~6 r- y- J+ ? if U(k,i)~=0; _/ T6 M/ X x; x9 d# {& C
break;end
2 y+ J* Q" r7 a! C+ H. j X( [ end) a6 W3 ?6 _3 S2 ^5 b& O1 e) X% _
for i=1:k+ N1 P% u- B$ P" C' M1 d7 l
a=U(i,k);U(i,k)=U(i,z);U(i,z)=a;
! T8 d" \: k6 g" g end
/ t6 d: e* a) x. \" @% P for i=1:n
1 _+ @" [9 K1 O, C2 Y9 G5 ~ a=A(i,k);A(i,k)=A(i,z);A(i,z)=a;
- n v7 w9 c' e! @ end: ~% e0 G2 N& g' T
end- w' P: j8 p7 c2 J
for i=k+1:n- ~( f; v/ f$ g' K2 u0 W
c=0;
7 Y) T5 a/ A; ]; N+ K. d for q=1:k-1
' i3 h5 B9 W2 q J1 w2 C: Y c=c+L(i,q)*U(q,k);, k6 ]' B3 W/ g
end8 V1 c# ]7 G2 i& G- C7 y1 R
L(i,k)=(A(i,k)-c)/U(k,k);* m# H, K( z0 s, p' U
end/ e6 }3 S4 i6 u5 k7 E- C) Z: b
end
9 K5 E# b/ i) L# \ for k=1:n
4 W( e$ b/ m; l# y7 ?% F" j c=0;, q5 z7 _" ?7 c. L; k6 [
for i=1:k-19 q$ b2 ~0 T: F( L
c=c+L(k,i)*y(i);
) H9 F& v% i& T5 W( T3 C, M+ r& Z end
( F2 X) r0 ^( D8 M7 G y(k)=(B(k)-c)/L(k,k);$ U# ~4 ~/ s8 E: `2 v) R
end
7 Q; j0 {/ i7 v: g/ e for k=n:-1:1
5 A+ J! t8 H! A, Q! k7 z/ P% a. j c=0;$ l) o! D- P# Q) K
for i=k+1:n ]' Z x( C; V1 W, [6 y
c=c+U(k,i)*x(i);
8 s# H# ^3 X9 l( c- { end, V# N, b- ], v
x(k)=(y(k)-c)/U(k,k);: [1 q5 E z; i' k) O- r9 ~. l
end
! _# d+ }9 u5 H3 l7 q5 P+ m& V6 ~. e- O" ~+ E+ G
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