public class Viterbi
{
public static void main(String[] args)
{
String[] states = {"Rainy", "Sunny"}; String[] observations = {"walk", "shop", "clean"}; double[] start_probability = {0.6, 0.4}; double[][] transition_probability = {{0.7, 0.3}, {0.4, 0.6}}; double[][] emission_probability = {{0.1, 0.4, 0.5}, {0.6, 0.3, 0.1}}; forward_viterbi(observations,states,start_probability,transition_probability,emission_probability);
} public static void forward_viterbi(String[] observations, String[] states,double[] start_probability, double[][] transition_probability, double[][] emission_probability) { int[][] path=new int[observations.length][states.length]; double[][] r=new double[observations.length][states.length]; for(int j=0;j<states.length;j++) { r[0][j]=start_probability[j]*emission_probability[j][0]; path[0][j]=0; } for(int t=1;t<observations.length;t++) { for(int i=0;i<states.length;i++) { double tmp=0;int m=0; for(int j=0;j<states.length;j++) { double tem=r[t-1][j]*transition_probability[j][i]*emission_probability[i][t]; if(tem>tmp) { tmp=tem; m=j; } } r[t][i]=tmp; path[t][i]=m; } } double p=0;int m=0; for(int i=0;i<r[0].length;i++) { if(r[r.length-1][i]>p) { p=r[r.length-1][i]; m=i; } } System.out.println("p="+p); int[] trace=new int[observations.length]; trace[observations.length-1]=m; for(int t=observations.length-1;t>0;t--) { trace[t-1]=path[t][m]; m=path[t][m]; } for(int i=0;i<trace.length;i++) System.out.println(states[trace[i]]); }
}銆?br />]]>