How to extract second attrbute from xml file line in R-CodePudding

I need to extract certain attributes from an xml file that has the same name of a node, but different number of attributes per node. The file is located here:

https://boardgamegeek.com//xmlapi//boardgame//13&type=boardgame,boardgameexpansion,boardgameaccesory,rpgitem,rpgissue,videogame&versions=1&stats=1&videos=1&marketplace=1&comments=1&pricehistory=1

And here is a small portion of the file itself:

<boardgames termsofuse="https://boardgamegeek.com/xmlapi/termsofuse">
  <boardgame objectid="13">
     <yearpublished>1995</yearpublished>
     <minplayers>3</minplayers>
     <maxplayers>4</maxplayers>
     <playingtime>120</playingtime>
     <minplaytime>60</minplaytime>
     <maxplaytime>120</maxplaytime>
     <age>10</age>
     <name sortindex="1">Catan</name>
     <name primary="true" sortindex="1">CATAN</name>
     <name sortindex="1">Catan (Колонизаторы)</name>
     <name sortindex="1">Catan telepesei</name>
     <name sortindex="1">Catan: Das Spiel</name>
     <name sortindex="1">Catan: Die Bordspel</name>
     <name sortindex="1">Catan: El Juego</name>
     <name sortindex="1">Catan: Gra planszowa</name>
     <name sortindex="1">Catan: Il Gioco</name>
     <name sortindex="1">Catan: Landnemarnir</name>

I want to extract only the value for "sortindex" from each line with "name" as the node name. I have tried the following, but it returns both the primary "true" and the sort index value for the second "name" node. I've tried so many different ways, and I can't get it to work. I've tried xmlGetAttr and others. How do I get this simple operation to work?

data <- read_xml(url)
xmlfile <- xmlParse(data)
xmltop = xmlRoot(xmlfile)
xmlSApply(getNodeSet(xmltop, '//name[@sortindex]'), xmlAttrs)

> xmlSApply(getNodeSet(xmltop, '//name[@primary]'), xmlAttrs)
             [,1]  
  primary   "true"
  sortindex "1"

CodePudding user response：

It sounds like you want to include any name node, even if it doesn't have the attribute. If so, you can try the following:

data <- read_xml('https://boardgamegeek.com//xmlapi//boardgame//13&type=boardgame,boardgameexpansion,boardgameaccesory,rpgitem,rpgissue,videogame&versions=1&stats=1&videos=1&marketplace=1&comments=1&pricehistory=1')
xmlfile <- xmlParse(data)
xmltop <- xmlRoot(xmlfile)

getAttr <- function(x, attrName) {
  attrs <- xmlAttrs(x)
  if (attrName %in% names(attrs)) {
    attrs[[attrName]]
  } else {
    NA
  }
}

xmlSApply(getNodeSet(xmltop, '//name'), function(x)getAttr(x, "sortindex"))

xmlSApply(getNodeSet(xmltop, '//name'), function(x)getAttr(x, "primary"))

If you don't want to include nodes without the attribute, then you can do something very similar:

library(xml2)
library(XML)


data <- read_xml('https://boardgamegeek.com//xmlapi//boardgame//13&type=boardgame,boardgameexpansion,boardgameaccesory,rpgitem,rpgissue,videogame&versions=1&stats=1&videos=1&marketplace=1&comments=1&pricehistory=1')
xmlfile <- xmlParse(data)
xmltop <- xmlRoot(xmlfile)


xmlSApply(getNodeSet(xmltop, '//name[@sortindex]'), function(x)xmlAttrs(x)[['sortindex']])

xmlSApply(getNodeSet(xmltop, '//name[@primary]'), function(x)xmlAttrs(x)[['primary']])