R：从XML获取属性值

我有一个XML，请参见下面的示例

<params>
<param id='1'>BEN</param>
<param id='2'>DAN</param>
<param id='3'>RYE</param>
    <param id='3'>RYE</param>
    <param id='3'>RYE</param>
</params>

---

谢谢。

您需要将函数

xpathApply

与参数

xmlValue

一起使用（以获取值，否则

xmlatrs

以获取属性）。路径应按以下语法给出：

“//tag[@attribute='value']”

---

xmlinfle谢谢您的回答。：）谢谢你的回答
inxml = xmlTreeParse(xmlinfile, handlers=list("comment"=function(x,...){NULL}), asTree = TRUE)
xmlList = xmlToList(inxml);
params = xmlList$'params'

a <- xmlParse('<params>
<param id='1'>BEN</param>
<param id='2'>DAN</param>
<param id='3'>RYE</param>
    <param id='3'>RYE</param>
    <param id='3'>RYE</param>
</params>')
xpathApply(a,"//param[@id='3']",xmlValue)
[[1]]
[1] "RYE"

[[2]]
[1] "RYE"

[[3]]
[1] "RYE"

xpathSApply(a,"//param[@id='3']",xmlValue)
[1] "RYE" "RYE" "RYE"

xmlinfile <- paste(readLines(n=7), collapse="\n")
<params>
  <param id='1'>BEN</param>
  <param id='2'>DAN</param>
  <param id='3'>RYE</param>
  <param id='3'>RYE</param>
  <param id='3'>RYE</param>
</params>
library(XML)
xpathApply(xmlParse(xmlinfile), "/params/param[@id='3']", xmlValue)  
# [[1]]
# [1] "RYE"
# 
# [[2]]
# [1] "RYE"
# 
# [[3]]
# [1] "RYE