Question

我正在尝试在Matlab中实现Viterbi算法，并且出于某种原因，在我的第一次传递之后我的感应部分将alpha变为0。 V =

0.7000         0
0.0980         0

V =

0.7000         0
     0         0

V =

0.7000         0
     0    0.1680

V =

0.7000         0
     0         0

另外，BestPath只会产生一堆0，最后只有一个，我不知道为什么。

我的代码：

function [ViterbiScore,BestPath] = Viterbi(A,B,Pi,Obv)

%INPUTS:
%Obv = Observation sequence
%A = Transition probability matrix
%B = Emission matrix
%Pi = initial probability matrix

%OUTPUT:
%ViterbiScore
%BestPath = Best-state sequence as a vector of complex numbers.

T=length(Obv);
N=length(A(1,:));

%Initilization
for i=1:N
    V(1,i)=Pi(i)*B(i,Obv(1));
    BT(1,i)=0;
end

%Induction
for t=2:T
    for j=1:N
        for i=1:N
            V(t,j)=max(V(t-1,i)*A(i,j))*B(j,Obv(t))
            [rndm,BT(t,j)]=max(V(t-1,i)*A(i,j));
        end
    end
end

%Termination
for i=1:N
    [ViterbiScore,BestPath(T)] = max(V(T,i));
end

for t=(T-1):1
    BestPath(t)=BT(t+1,BestPath(t+1));
end

维特比算法Matlab

0 个答案: