R/pvsRequest5.R

In pvsR: An R package to interact with the Project Vote Smart API for scientific research

pvsRequest5 <-
function (request,inputs) {
  pvs.url <- paste("http://api.votesmart.org/",request,"key=",get('pvs.key',envir=.GlobalEnv),inputs,sep="") #generate url for request
  
  httpresp <- GET(url=pvs.url)
  xmltext <- content(x=httpresp, as="text")
  errors <-  getXMLErrors(xmltext) # check if xml can be parsed properly
  
  if (length(errors) != 0) {
    
    if (names(errors[[1]]$code) == "XML_ERR_CDATA_NOT_FINISHED") { # if not, try to fix 
      
      xmltext <- gsub(pattern="\003", replacement="", x=xmltext, fixed=TRUE)
      
    }
  }
  
  output.base <- xmlRoot(xmlTreeParse(xmltext, useInternalNodes=TRUE))
  
  
  
  if (names(output.base)[1]=="errorMessage") {
    
    # if the requested data is not available, return an empty (NA) data frame and give a warning
    warning(gsub(pattern="&", replacement=" ", x=paste("No data available for: ", inputs,". The corresponding rows in the data frame are filled with NAs.", sep=""), fixed=TRUE), call.=FALSE)
    
    
    output.df <- data.frame(matrix(nrow=1,ncol=0))
    output.df
    
    
  } else {
    
    # alternative: check if there are subnodes, if not, remove mainnode
    
    output <- removeChildren(output.base,kids=1)
    
    subnames <- xmlSApply(output, function(x) length(names(x))) # get vector with number of names in subnodes
    
    if (length(subnames[subnames==0])==0) {
      
      
      subnames <- xmlSApply(output, function(x) names(x))
      
      notimp <- names(subnames[subnames=="text"])
      
      output <- removeChildren(output,notimp)
      
      output2 <- t(xmlSApply(output, FUN=function(x) xmlSApply(x,xmlValue)))
      
    } else {
      
      
      
      notimp <- names(subnames[subnames==0])
      
      output <- removeChildren(output,notimp)
      
      output2 <- t(xmlSApply(output, FUN=function(x) xmlSApply(x,xmlValue)))
      
      
      
      
    }
    
    output.df <- data.frame(output2, row.names=NULL) 
    output.df
    
  }
}