In R, how can I loop over repeated XML nodes, and save text values in a list?

Question

I\'m working with XML files from clinicaltrials.gov, which have a structure like this:

  ...
  
  ...
  

        

Answer 1

Here is an example

 ns <- getNodeSet(xml, '//clinical_results/outcome_list/outcome/analysis_list/analysis/method')
 element_cnt <-length(ns))
 strings<-paste(sapply(ns, function(x) { xmlValue(x) }),collapse="|"))

Answer 2

This code will put a subset of nodes that correspond to <location> from a clinical trial into a data frame:

library(XML)
clinicalTrialUrl <- "http://clinicaltrials.gov/ct2/show/NCT01480479?resultsxml=true"
xmlDoc <- xmlParse(clinicalTrialUrl, useInternalNode=TRUE)
locations <- xmlToDataFrame(getNodeSet(xmlDoc,"//location"))

In this case there are 221 locations. However, the code assumes sort of a flat structure and lumps subnodes together. For example, anything under <facility> gets concatenated into a single string. I can go into the subnodes and put them one by one into a dataframe.

Answer 3

I don't understand why do you not use again xpathSApply, to retrieve locations as you already did for titles?!

xpathSApply(xml_doc, "//clinical_study/location" , xmlValue)