Question

我在R中使用bnlearn包来训练贝叶斯网络。我有以下代码的麻烦（稍微修改了bnlearn示例代码）：

library(bnlearn)
data(learning.test)
fitted = bn.fit(hc(learning.test), learning.test)

myfuncBN=function(){

  var = names(learning.test)
  obs = 2
  str = paste("(", names(learning.test)[-3], "=='",
          sapply(learning.test[obs,-3], as.character), "')",
          sep = "", collapse = " & ")
  str2 = paste("(", names(learning.test)[3], "=='",
           as.character(learning.test[obs, 3]), "')", sep = "")
  cpquery(fitted, eval(parse(text = str2)), eval(parse(text = str)))
}

myfuncBN()

此代码抛出错误：

包装错误：无法强制类型＆＃39;关闭＆＃39;到＃＆＃39;字符＆＃39;

的矢量

但是如果在函数myfuncBN（）之外定义了str和str2，则它可以工作。有谁知道这个的原因？

Answer 1

以下是问题的解决方案：

library(bnlearn)
data(learning.test)
fitted = bn.fit(hc(learning.test), learning.test)

myfuncBN=function() {
  vars = names(learning.test)
  obs = 2
  str1 = paste("(", vars[-3], "=='",
          sapply(learning.test[obs,-3], as.character), "')",
          sep = "", collapse = " & ")
  str2 = paste("(", vars[3], "=='",
           as.character(learning.test[obs, 3]), "')", sep = "")

  eval(parse(text=paste("cpquery(fitted,",str2,",",str1,")")))
}

set.seed(1)
myfuncBN()

# [1] 0.05940594

此值等于：

给出的结果

set.seed(1)
cpquery(fitted, event=(C=="c"), 
             evidence=((A=="b") & (B=="a") & (D=="a") & (E=="b") & (F=="b")))

# [1] 0.05940594

R bnlearn eval内部功能

1 个答案: