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数学中国总编辑
TA的每日心情 | 衰 2016-11-18 10:46 |
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签到天数: 206 天 [LV.7]常住居民III 超级版主
群组: 2011年第一期数学建模 群组: 第一期sas基础实训课堂 群组: 第二届数模基础实训 群组: 2012第二期MCM/ICM优秀 群组: MCM优秀论文解析专题 |
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发表于 2011-11-28 10:48
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matlab下面的kalman滤波程序2 D* p2 K+ W9 m" h
clear N=200; w(1)=0;
" [4 g& c. i" ?0 p* m4 p* t. Ow=randn(1,N) $ j4 y3 N% c+ z z; f
x(1)=0; 0 `' o( k; I$ l5 G$ p3 J9 J8 m9 U. l
a=1; - W/ P8 |/ @; O; I5 b$ i
for k=2:N;
' J* J) |7 `/ X! `% M; bx(k)=a*x(k-1)+w(k-1);
& n/ P' ~# x( @! Lend ; p- \/ M8 h1 i+ G2 @$ k
V=randn(1,N); , A+ t' T D' Y( Q) Q1 w
q1=std(V);
. G2 F9 ^, E1 E3 g' H- R. ?Rvv=q1.^2; - {2 C' M0 E( X/ J
q2=std(x);
. V$ y. F# M% L9 T; O4 Z! j2 CRxx=q2.^2; ; B2 @+ r" v: e; h, `! ]
q3=std(w); . ?0 n1 k) T: r" m S
Rww=q3.^2; ( M5 o: ?/ C+ N
c=0.2; ' l6 c' L' h0 \
Y=c*x+V;
8 }$ q+ c( n' _% g7 J" ap(1)=0;
: x l$ @& c5 s4 qs(1)=0;
* l" Z! R* X* n% ^for t=2:N;
0 X$ z9 M% s: {9 U1 p/ [p1(t)=a.^2*p(t-1)+Rww;
( k) `# k4 X V# K, T8 D1 S- sb(t)=c*p1(t)/(c.^2*p1(t)+Rvv); 5 u$ Y+ i5 q. r9 S) ^: t. F6 ?: N
s(t)=a*s(t-1)+b(t)*(Y(t)-a*c*s(t-1)); 1 k, a4 D/ p; F) D0 S
p(t)=p1(t)-c*b(t)*p1(t); % O" A5 n7 S5 V6 S& ~) |5 q* U w
end 7 T4 T3 _+ P8 c, m# i$ A/ E
t=1:N;
! m+ Z; R1 ~, i2 @* jplot(t,s,'r',t,Y,'g',t,x,'b'); * u/ q+ Y4 Q: a9 T
function [x, V, VV, loglik] = kalman_filter(y, A, C, Q, R, init_x, init_V, varargin) 1 t7 \" j( E% O/ A
% Kalman filter. 5 y0 p3 S/ L' P7 q* U
% [x, V, VV, loglik] = kalman_filter(y, A, C, Q, R, init_x, init_V, ...) 5 v8 A- N" z* R* u
% / M2 \ q/ z; T: Y
% INPUTS:
, P4 z/ q- R# |) |4 }% y(:,t) - the observation at time t ! U( G) Z' d+ N- w
% A - the system matrix . z# x! ]' _" F* l4 a6 v5 {
% C - the observation matrix % F& `7 A1 x' D+ g5 X9 r
% Q - the system covariance 3 X Q! J5 D. {. r. M! H+ @
% R - the observation covariance
; H8 [7 c/ [* V5 P1 {" {8 Y% init_x - the initial state (column) vector ( i* M: Z' I8 b3 I% Q% \3 G
% init_V - the initial state covariance
9 l. ?3 W% A5 s2 V' l% k& F% C+ k; ~ Y8 U/ l) e: {& f
% OPTIONAL INPUTS (string/value pairs [default in brackets])
/ ]* \+ p, |* h o2 E" h# o' e% 'model' - model(t)=m means use params from model m at time t [ones(1,T) ] 5 A6 k: S0 ]! j* c( h$ E. b
% In this case, all the above matrices take an additional final dimension,
( R" a, t7 j u' s% i.e., A(:,:,m), C(:,:,m), Q(:,:,m), R(:,:,m). ; i2 [$ I7 ^1 v* _+ |
% However, init_x and init_V are independent of model(1).
. s1 ?; ~+ z% S% l9 {' r `% 'u' - u(:,t) the control signal at time t [ [] ] 5 M' |6 y0 m4 S- d
% 'B' - B(:,:,m) the input regression matrix for model m
) g2 ?0 E! f6 T4 S% 1 d% z* s, v5 U. E5 b2 W' W
% OUTPUTS (where X is the hidden state being estimated)
$ i; \: H% T) Y. g8 W# n+ q% x(:,t) = E[X(:,t) | y(:,1:t)] X0 N& ^) I O; _1 q
% V(:,:,t) = Cov[X(:,t) | y(:,1:t)] |* G; Q, Z8 H# ]* @* H
% VV(:,:,t) = Cov[X(:,t), X(:,t-1) | y(:,1:t)] t >= 2 8 z* {6 [1 r8 m- F1 h; h
% loglik = sum{t=1}^T log P(y(:,t))
6 g! I8 `" p. y2 [( Y%
: L' M% p. H- q9 P! Y3 \; t6 b% If an input signal is specified, we also condition on it: - k0 R% Z- P+ F- i# [2 O6 R9 p
% e.g., x(:,t) = E[X(:,t) | y(:,1:t), u(:, 1:t)] " H0 c: v# k5 z; J
% If a model sequence is specified, we also condition on it: 1 ?2 K4 M/ b9 ~2 V: \7 ^
% e.g., x(:,t) = E[X(:,t) | y(:,1:t), u(:, 1:t), m(1:t)]
4 O. G7 n4 z9 i' P# e[os T] = size(y); 2 J# e# c$ [/ w! O# ^- l% ~
ss = size(A,1); % size of state space
) J2 D' M3 j( x; T% set default params
( p" W" O$ c; t; Amodel = ones(1,T); # I r, l. r2 @5 H1 F Y
u = [];
1 ~' c: s ]7 O' T# {3 oB = [];
2 _+ a$ L* D# E" r9 j/ Sndx = [];
" ]1 C) S9 e4 b' |* `* }. r( I" Qargs = varargin; $ H7 ^4 I# L' F4 s( h( [
nargs = length(args);
& Y; q M' @8 B" q$ j, Ifor i=1:2:nargs ) m' [5 E9 F8 ]
switch args
9 [8 z9 a: ?0 s7 N- P. r+ j( b" h8 [4 ccase 'model', model = args{i+1}; ) T! Z3 N- l# } p7 Y8 w
case 'u', u = args{i+1}; 8 |6 u( C4 G! H1 Z# B( U2 L* M7 W
case 'B', B = args{i+1}; ( f/ _' {7 E2 Q9 q# g. G6 c
case 'ndx', ndx = args{i+1};
* y6 _0 c0 m& Potherwise, error(['unrecognized argument ' args]) / b$ i1 h1 S6 f( D0 c& E0 m
end
' V/ s; `' u' K5 e) |0 hend 3 [0 a* Q( X* O* h$ T0 T
x = zeros(ss, T);
# B0 P1 r5 F7 t" y. oV = zeros(ss, ss, T);
% e! M$ v0 W4 o2 J. N6 V2 EVV = zeros(ss, ss, T); ( k/ B! a0 S" R0 E; B) q) R* p+ Y3 Z* `
loglik = 0; & \7 I9 i, [3 v6 K5 d
for t=1:T m = model(t);
, l& z! M2 R. N& T3 U: Cif t==1 %prevx = init_x(:,m);
; G& X0 G; b9 D5 a1 C%prevV = init_V(:,:,m); + G: E, {1 @ L/ S0 S$ `
prevx = init_x; 5 ^/ ^' v4 F$ x1 ^2 |
prevV = init_V;
% O4 z! C8 _8 ]) u0 finitial = 1; + R' X( X* g! t8 I% P( u' Y$ }9 T
else prevx = x(:,t-1);
; T5 J1 L; r" N6 c& gprevV = V(:,:,t-1); 2 d( H. N2 U0 y" j5 s
initial = 0; * W% |7 r% `; S; |! L7 x
end
2 a7 D4 R7 d$ W9 E! Mif isempty(u) 3 L5 b; W: U( c" o
[x(:,t), V(:,:,t), LL, VV(:,:,t)] = ...
5 b1 W0 E1 i5 w/ ]2 _, ~kalman_update(A(:,:,m), C(:,:,m), Q(:,:,m), R(:,:,m), y(:,t), prevx, prevV, 'initial', initial); else
/ ~* ?0 x! t: |$ p* a% z3 u/ r1 ? if isempty(ndx) [x(:,t), V(:,:,t), LL, VV(:,:,t)] = ...
- X& A( p1 y& Y/ W2 i2 M/ L kalman_update(A(:,:,m), C(:,:,m), Q(:,:,m), R(:,:,m), y(:,t), prevx, prevV, ... 'initial', initial, 'u', u(:,t), 'B', B(:,:,m));
- K" l0 }' T* Q3 _. belse
/ u9 N: _; U9 Si = ndx; $ Y2 v; H) @+ e. ]
% copy over all elements; only some will get updated x(:,t) = prevx; ) y4 o% q- X8 k3 [7 x* R& |
prevP = inv(prevV);
! R" u3 E9 }7 L- A- L; G/ KprevPsmall = prevP(i,i);
0 t: m2 _6 P) d: G: ]7 BprevVsmall = inv(prevPsmall);
/ b# R; u0 n; M[x(i,t), smallV, LL, VV(i,i,t)] = ... kalman_update(A(i,i,m), C(:,i,m), Q(i,i,m), R(:,:,m), y(:,t), prevx(i), prevVsmall, ... 'initial', initial, 'u', u(:,t), 'B', B(i,:,m));
1 A/ M9 d" R" |' xsmallP = inv(smallV); $ S% p" {) Q$ V/ z' a
prevP(i,i) = smallP; . j) g7 N1 C+ J8 N" x' a4 e
V(:,:,t) = inv(prevP);
# b: S: x+ F; b: Z8 @/ |3 Uend
! e2 u% g$ w2 d3 v$ {4 U5 I1 ?! Tend 9 C( `0 G0 _6 N; o
loglik = loglik + LL; 5 d: @5 Q* R) Z6 N
end |
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