How to read data into a data.frame for Baltimore City 311 system.

gistfile1.txt

rm(list=ls())
library(XML)
library(RJSONIO)
library(stringr)

ff <- url("http://311.baltimorecity.gov/open311/v2/requests.json?api&jurisdiction_id=baltimorecity.gov")
x <- readLines(ff)
close(ff)
J <- fromJSON(x, asText=TRUE )

  cnames <- c("service_request_id", "token", "status","service_name", "service_code", "description", "requested_datetime", "updated_datetime", "lat", "long", "address", "status_notes")
J <- lapply(J, function(x) {
	if (! "address" %in% names(x)) x <- c(x, address=NA)
	if (! "status_notes" %in% names(x)) x <- c(x, status_notes=NA)
	x <- x[!names(x) %in% "media_url"]
	x <- x[cnames]
	x
	})
data <- data.frame(do.call("rbind", J), stringsAsFactors=FALSE)
for (icol in cnames) {
	x <- data[, icol] 
	if (class(x) == "list") {
		#print(icol)
		x <- sapply(x, function(dd) ifelse(is.null(dd), NA, dd))
		data[, icol] <- unlist(x)
	}
	data[,icol][data[,icol] == ""] <- NA
}