概率图模型 基于R语言 这本书中的第一个R语言程序

概率图模型 基于R语言 这本书中的第一个R语言程序

 prior <- c(working =0.99,broken =0.01)
 likelihood <- rbind(working = c(good=0.99,bad=0.01),broken =c(good=0.6,bad=0.4))
 data <- c("bad","bad","bad","bad")

 bayes <- function(prior, likelihood, data)
 {
     posterior <- matrix(0, nrow=length(data), ncol=length(prior))
     dimnames(posterior) <- list(data, names(prior))

     initial_prior = prior
     for(i in 1:length(data))
     {
         posterior[i, ] <-
             prior*likelihood[ , data[i]]/
             sum(prior * likelihood[ , data[i]])

         prior <- posterior[i , ]
     }

     return(rbind(initial_prior,posterior))
 }

 bayes(prior,likelihood,data)
 matplot(bayes(prior,likelihood,data),t='b',lty =1,pch =20,col =c(3,2))

运行效果