xmlTreeParse不识别树

Question

I have a simple question. I'm trying to get a list of the indicators available on the Open data api. I use the RCurl function getURL to pull the contents of http://api.worldbank.org/indicators , and then the XML function xmlTreeParse on the resulting xml page. But xmlTreeParse just treats the xml file as a big block of test. Why is this? Thanks!

library(RCurl)
library(XML)

temp <- getURL("http://api.worldbank.org/indicators)
temp <- xmlTreeParse(temp)

Answer 1

You can use

temp <- getURL("http://api.worldbank.org/indicators")
temp <- xmlParse(temp)
xpathSApply(temp,"//wb:source") # example access data 1
xpathSApply(temp,"//wb:source[@id=2]") # example access data 2

use xmlParse or xmlTreeParse(useInternalNodes=T)

with this simple structure you can transform to a dataframe as follows

my.df<-xmlToDataFrame(temp)

or a list

my.list<-xmlToList(temp)

> my.list[[1]]
$name
[1] "Agricultural machinery, tractors"

$source
$source$text
[1] "World Development Indicators"

$source$.attrs
 id 
"2" 


$sourceNote
[1] "Agricultural machinery refers to the number of wheel and crawler tractors (excluding garden tractors) in use in agriculture at the end of the calendar year specified or during the first quarter of the following year."

$sourceOrganization
[1] "Food and Agriculture Organization, electronic files and web site."

$topics
$topics$topic
$topics$topic$text
[1] "Agriculture & Rural Development  "

$topics$topic$.attrs
 id 
"1" 



$.attrs
              id 
"AG.AGR.TRAC.NO"