Question

我有一个XML，请参阅下面的示例

<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>

如何获得属性为id = 3的所有参数？

以下是我到目前为止所做的：xmlinfile是XML文件

inxml = xmlTreeParse(xmlinfile, handlers=list("comment"=function(x,...){NULL}), asTree = TRUE)
xmlList = xmlToList(inxml);
params = xmlList$'params'

非常感谢。

Answer 1

您需要使用带有参数xpathApply的函数xmlValue（获取值，否则xmlAttrs获取属性）。路径应使用以下语法给出："//tag[@attribute='value']"。

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"

同样，xpathSApply会在可能的情况下为您提供值向量：

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

Answer 2

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

R：从XML获取属性值

2 个答案: