R/pvsRequest7.1.R

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

pvsRequest7 <-
	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 {

			output <- output.base
			nodenames <- unique(names(output)) # get names of nodes
			freq.names <- summary(as.factor(names(output))) # check frequency,
			freq.subnames <- sapply(names(output), FUN=function(x) sum(summary(as.factor(names(output[[x]]))) )  )
			
			# if the subnodes have more than one entry (child) scrap them (individually), then cbind
			nodenames <- nodenames[nodenames!="generalInfo"]
			nodenames <- nodenames[nodenames!="generalinfo"]
			
			if (length(unique(names(output)))>1) {
				output.list <- lapply(nodenames, FUN=function(i) {
					if (freq.subnames[[i]]>1) {
						x <- output[[i]]
						data.frame(t(xmlSApply(x, xmlValue)), stringsAsFactors = FALSE)
					} else {
						NA
					}
				})

				output.df <- bind_cols(output.list)
				return(output.df)

			} else {
				output <- t(xmlSApply(removeChildren(output.base,kids=1), function(x) xmlSApply(x, xmlValue)))
				output.df <- data.frame(output, row.names=NULL, stringsAsFactors = FALSE)
				
				return(output.df)
			}
		}
	}