I need to find and combine information in some huge XML-files (doc <- xmlInternalTreeParse(file.name, useInternalNodes=TRUE, trim=TRUE) causes my 16GB computer to start swapping to disk before finishing), and have followed the good instructions on http://www.omegahat.org/RSXML/Overview.html.
Adding to the example from there, this is more or less what my file looks like:
<?xml version="1.0" ?>
<TABLE>
<SCHOOL>
<NAME> School1 </NAME>
<GRADES>
<STUDENT> Fred </STUDENT>
<TEST1> 66 </TEST1>
<TEST2> 80 </TEST2>
<FINAL> 70 </FINAL>
</GRADES>
<TEAMS>
<SOCCER> SoccerTeam1 </SOCCER>
<HOCKEY> HockeyTeam1 </HOCKEY>
</TEAMS>
</SCHOOL>
<SCHOOL>
<NAME> School2 </NAME>
<GRADES>
<STUDENT> Wilma </STUDENT>
<TEST1> 97 </TEST1>
<TEST2> 91 </TEST2>
<FINAL> 98 </FINAL>
</GRADES>
<TEAMS>
<SOCCER> SoccerTeam2 </SOCCER>
</TEAMS>
</SCHOOL>
</TABLE>
I need to list students per school with hockey-team, and the team-names. The wanted output from the example should be "Fred", "HockeyTeam1", "School1". The real example have thousands of "schools", "hockey teams" and "players".
How can I use xmlEventParse to parse the files to extract the info? I tried to extract all text-fields from the files, but after hours of waiting there was still no output. Note: The real files are more nested than this, so it is not enought to step fixed levels to find info.
Steps for Merging XML Files in Java PDF for Java APIs can be done with just few lines of code. Create object of PdfFileEditor class. Create the array of all files that will be merged. Use concatenate() method to merge all files.
We'll use the XML package
library(XML)
and create a closure that contains a function to handle the 'SCHOOL' node, as well as two helper functions to retrieve results when done. The SCHOOL function is invoked on each SCHOOL node. If it finds a hockey team, it uses the /SCHOOL/NAME/text() as a 'key', and the /SCHOOL/TEAMS/HOCKEY/text() and //STUDENT/text() (or /SCHOOL/GRADES/STUDENT/text()) as values. A message is printed for every 100 (by default) schools with hockey teams, so that there's some indication of progress. The 'get' function is used after the fact to retrieve the result.
teams <- function(progress=1000) {
res <- new.env(parent=emptyenv()) # for results
it <- 0L # iterator -- nodes visited
list(SCHOOL=function(elt) {
## handle 'SCHOOL' nodes
if (getNodeSet(elt, "not(/SCHOOL/TEAMS/HOCKEY)"))
## early exit -- no hockey team
return(NULL)
it <<- it + 1L
if (it %% progress == 0L)
message(it)
school <- getNodeSet(elt, "string(/SCHOOL/NAME/text())") # 'key'
res[[school]] <-
list(team=getNodeSet(elt,
"normalize-space(/SCHOOL/TEAMS/HOCKEY/text())"),
students= xpathSApply(elt, "//STUDENT", xmlValue))
}, getres = function() {
## retrieve the 'res' environment when done
res
}, get=function() {
## retrieve 'res' environment as data.frame
school <- ls(res)
team <- unlist(eapply(res, "[[", "team"), use.names=FALSE)
student <- eapply(res, "[[", "students")
len <- sapply(student, length)
data.frame(school=rep(school, len), team=rep(team, len),
student=unlist(student, use.names=FALSE))
})
}
We use the function as
branches <- teams()
xmlEventParse("event.xml", handlers=NULL, branches=branches)
branches$get()
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