R/District.getByZip.R

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

##' Get district IDs according to the zip code
##' 
##' This function is a wrapper for the District.getByZip() method of the PVS API District class which grabs district IDs according to the ZIP code. The function sends a request with this method to the PVS API for all ZIP codes given as a function input, extracts the XML values from the returned XML file(s) and returns them arranged in one data frame.
##' @usage District.getByZip(zip5, zip4=NULL)
##' @param zip5 a character string or list of character strings with the five-digit ZIP code
##' @param zip4 (optional) a character string or list of character strings with the expanded ZIP+4 code (default: All)
##' @return A data frame with a row for each district and columns with the following variables describing the district:\cr districtList.district*.districtId,\cr districtList.district*.name,\cr districtList.district*.officeId,\cr districtList.district*.stateId.
##' @references http://api.votesmart.org/docs/District.html\cr
##' See also: Matter U, Stutzer A (2015) pvsR: An Open Source Interface to Big Data on the American Political Sphere. PLoS ONE 10(7): e0130501. doi: 10.1371/journal.pone.0130501
##' @author Ulrich Matter <ulrich.matter-at-unibas.ch>
##' @examples
##' # First, make sure your personal PVS API key is saved as an option
##' # (options("pvs.key" = "yourkey")) or in the pvs.key variable:
##' \dontrun{pvs.key <- "yourkey"}
##' # get district IDs by ZIP Code
##' \dontrun{district <- District.getByZip(list(10001,10002))}
##' \dontrun{district}
##' @export

District.getByZip <-
	function (zip5, zip4=NULL) {
		
		if (length(zip4)==0) {
			# internal function
			District.getByZip.basic1 <- function (.zip5) {
				
				request <-  "District.getByZip?"
				inputs  <-  paste("&zip5=",.zip5,sep="")
				pvs.key <- getPVS_key()
        pvs.url <- paste("http://api.votesmart.org/",request,"key=",pvs.key,inputs,sep="") #generate url for request
				
				output.base <- xmlRoot(xmlTreeParse(pvs.url, useInternalNodes=TRUE))
				districts <-  removeChildren(output.base, kids=list(1,2))
				if ("electionDistricts" %in% names(districts)){
					electionDistricts <- districts[["electionDistricts"]]
					districts <- removeChildren(districts, kids=list("electionDistricts"))
					output.electionDistricts <- data.frame(t(xmlSApply(electionDistricts, function(x) xmlSApply(x, xmlValue))), row.names=NULL, stringsAsFactors = FALSE)
					output.electionDistricts$Type <- "electionDistrict"
				} else {
					output.electionDistricts <- data.frame(zip5=.zip5, Type="electionDistrict", stringsAsFactors = FALSE)
				}
				output.districts <- data.frame(t(xmlSApply(districts, function(x) xmlSApply(x, xmlValue))), row.names=NULL, stringsAsFactors = FALSE)
				output.districts$Type <- "district"
				
				output <- bind_rows(list(output.districts, output.electionDistricts))      
				output$zip5 <- .zip5
				
				return(output)
			}
			
			# Main function  
			output.list <- lapply(zip5, FUN= function (s) {
				District.getByZip.basic1(.zip5=s)
			}
			)

			output.list <- redlist(output.list)
			output <- bind_rows(output.list)

		} else {
			
			# internal function
			District.getByZip.basic2 <- function (.zip5, .zip4) {
				pvs.key <- getPVS_key()
        pvs.url <- paste("http://api.votesmart.org/",request,"key=",pvs.key,inputs,sep="") #generate url for request

				request <-  "District.getByZip?"
				inputs  <-  paste("&zip5=",.zip5, "&zip4=", .zip4, sep="")
				
				output.base <- xmlRoot(xmlTreeParse(pvs.url, useInternalNodes=TRUE))
				districts <-  removeChildren(output.base, kids=list(1,2))
				if ("electionDistricts" %in% names(districts)){
					electionDistricts <- districts[["electionDistricts"]]
					districts <- removeChildren(districts, kids=list("electionDistricts"))
					output.electionDistricts <- data.frame(t(xmlSApply(electionDistricts, function(x) xmlSApply(x, xmlValue))), row.names=NULL, stringsAsFactors = FALSE)
					output.electionDistricts$Type <- "electionDistrict"
				} else {
					output.electionDistricts <- data.frame(zip4=.zip4, Type="electionDistrict", stringsAsFactors = FALSE)
				}
				
				output.districts <- data.frame(t(xmlSApply(districts, function(x) xmlSApply(x, xmlValue))), row.names=NULL, stringsAsFactors = FALSE)
				output.districts$Type <- "district"

				output <- bind_rows(list(output.districts, output.electionDistricts))      
				output$zip5 <- .zip5
				output$zip4 <- .zip4
				
				return(output)
			}
			
			# Main function  
			output.list <- lapply(zip5, FUN= function (s) {
				lapply(zip4, FUN= function (c) {
					District.getByZip.basic2( .zip5=s, .zip4=c)
				}
				)
			}
			)
			
			output.list <- redlist(output.list)
			output <- bind_rows(output.list)
		}
		return(output)
	}