xml - 如何从 xml 文件创建 R 数据框？

Question

我有一个 XML 文档文件。该文件的一部分如下所示:

-<attr>  
     <attrlabl>COUNTY</attrlabl>  
     <attrdef>County abbreviation</attrdef>  
     <attrtype>Text</attrtype>  
     <attwidth>1</attwidth>  
     <atnumdec>0</atnumdec>  
    -<attrdomv>  
        -<edom>  
            <edomv>C</edomv>  
            <edomvd>Clackamas County</edomvd>  
            <edomvds/>  
         </edom>  
        -<edom>  
            <edomv>M</edomv>  
            <edomvd>Multnomah County</edomvd>  
            <edomvds/>  
         </edom>  
        -<edom>  
            <edomv>W</edomv>  
            <edomvd>Washington County</edomvd>  
            <edomvds/>  
         </edom>  
     </attrdomv>  
 </attr>

从这个 XML 文件中，我想创建一个包含 attrlabl、attrdef、attrtype 和 列的 R 数据框>属性。请注意，attrdomv 列应包含类别变量的所有级别。数据框应如下所示:

attrlabl    attrdef                attrtype    attrdomv  
COUNTY      County abbreviation    Text        C Clackamas County; M Multnomah County; W Washington County  

我有这样一个不完整的代码:

doc <- xmlParse("taxlots.shp.xml")  
dataDictionary <- xmlToDataFrame(getNodeSet(doc,"//attrlabl"))  

你能完成我的 R 代码吗？感谢您的帮助!

Answer 1

假设这是正确的 taxlots.shp.xml 文件:

<attr>  
     <attrlabl>COUNTY</attrlabl>  
     <attrdef>County abbreviation</attrdef>  
     <attrtype>Text</attrtype>  
     <attwidth>1</attwidth>  
     <atnumdec>0</atnumdec>  
    <attrdomv>  
        <edom>  
            <edomv>C</edomv>  
            <edomvd>Clackamas County</edomvd>  
            <edomvds/>  
         </edom>  
        <edom>  
            <edomv>M</edomv>  
            <edomvd>Multnomah County</edomvd>  
            <edomvds/>  
         </edom>  
        <edom>  
            <edomv>W</edomv>  
            <edomvd>Washington County</edomvd>  
            <edomvds/>  
         </edom>  
     </attrdomv>  
 </attr>

你快到了:

doc <- xmlParse("taxlots.shp.xml")
xmlToDataFrame(nodes=getNodeSet(doc1,"//attr"))[c("attrlabl","attrdef","attrtype","attrdomv")]
  attrlabl             attrdef attrtype                                             attrdomv
1   COUNTY County abbreviation     Text CClackamas CountyMMultnomah CountyWWashington County

但是最后一个字段没有你想要的格式。为此，需要一些额外的步骤:

step1 <- xmlToDataFrame(nodes=getNodeSet(doc1,"//attrdomv/edom"))
step1
  edomv            edomvd edomvds
1     C  Clackamas County        
2     M  Multnomah County        
3     W Washington County  

step2 <- paste(paste(step1$edomv, step1$edomvd, sep=" "), collapse="; ")
step2
[1] "C Clackamas County; M Multnomah County; W Washington County"

cbind(xmlToDataFrame(nodes= getNodeSet(doc1, "//attr"))[c("attrlabl", "attrdef", "attrtype")],
      attrdomv= step2)
  attrlabl             attrdef attrtype                                                      attrdomv
1   COUNTY County abbreviation     Text C Clackamas County; M Multnomah County; W Washington County