R/pvsRequest5.R

In umatter/pvsR: Interact with the Project Vote Smart API for Scientific Research

pvsRequest5 <-
	function (request,inputs) {
		pvs.key <- getPVS_key()
    pvs.url <- paste("http://api.votesmart.org/",request,"key=",pvs.key,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), stringsAsFactors = FALSE)
			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, stringsAsFactors = FALSE) 
			
			return(output.df)
		}
	}