R/get_dataset.R

In SandroGroth/esriOpenData: esriOpenData

#' Load data into R Environment
#'
#' \code{get_dataset} retrieves the actual data of a selected dataset from the histing server.
#' The data can be subsetted by providing a vector containing only the needed field names. To
#' store the subsetted dataset persistently in the specified output directory, the export option
#' should be set to TRUE.
#'
#' @param sel_dataset Dataframe, containing the information of a selected dataset.
#' @param fields Vector of characters, containing field names that should be included in the imported subset.
#' @param sp_ref Numeric. An EPSG code of a desired Spatial reference. Default is 4326.
#' @param export Logical, wheter the imported subset should be exported to the output directory or not.
#' @param format Character. If export is TRUE, which export format should be used. Options are "shp", "kml", "csv".
#'
#' @return Spatial Object. Ready to use spatial object of the selected dataset with all filters applied.
#'
#' @examples
#' datasets <- search_datasets("Zensus 2011", aoi = TRUE)
#' sel_dataset <- select_dataset(datasets, 1)
#' ## checkout available fields
#' fields(sel_dataset)
#' age1829 <- get_dataset(sel_dataset, c("OBJECTID", "NAME", "ALTER_1"), export = T, format = "csv")
#'
#' @author Sandro Groth
#'
#' @importFrom urltools param_set
#' @importFrom rgdal readOGR
#' @importFrom rgdal writeOGR
#'
#' @keywords get_dataset
#' @export

get_dataset <- function(sel_dataset, fields=FALSE, sp_ref=4326, export=FALSE, format="shp") {
  if(!is.data.frame(sel_dataset)) {msg("sel_dataset has to be of type data.frame.", "ERROR")}
  if(!isFALSE(fields) & !is.vector(fields)) {msg("fields has to be FALSE or a vector.", "ERROR")}
  if(!is.numeric(sp_ref)) {msg("sp_ref has to be of type numeric.", "ERROR")}
  if(!is.logical(export)) {msg("export has to be of type logical.", "ERROR")}
  if(!"id" %in% colnames(sel_dataset)) {msg("sel_dataset has no column 'id'.", "ERROR")}
  if(!"url" %in% colnames(sel_dataset)) {msg("sel_dataset has no column 'url'.", "ERROR")}
  if(!"fields" %in% colnames(sel_dataset)) {msg("sel_dataset has no column 'fields'.", "ERROR")}
  if(!format %in% c("shp", "csv", "kml")) {msg("Supported formats are only: shp, csv, kml", "ERROR")}
  if(!sel_dataset$dataType == "Layer") {msg(paste0("selected datatype is currently not supported: ", sel_dataset$dataType), "ERROR")}

  rest_url <- sel_dataset$url
  id <- sel_dataset$id
  ds_fields <- sel_dataset$fields[[1]]$name
  slug <- sel_dataset$slug

  query_fields = "*"
  if(!isFALSE(fields)) {
    query_fields <- ""
    for(i in 1:length(fields)) {
      if(!fields[i] %in% ds_fields) {msg(paste0(fields[i], " is not a field in the specified dataset.", "ERROR"))}
      if(query_fields != "") {
        query_fields <- paste0(query_fields, ",", fields[i])
      } else {
        query_fields <- fields[i]
      }
    }
  }

  where_clause <- "1%3D1"
  rest_url <- paste0(URLencode(rest_url), "/query")
  rest_url <- urltools::param_set(rest_url, "outFields", URLencode(query_fields))
  rest_url <- urltools::param_set(rest_url, "where", URLencode(where_clause))
  rest_url <- urltools::param_set(rest_url, "outSR", sp_ref)
  rest_url <- urltools::param_set(rest_url, "f", "json")

  msg(paste0("Requesting URL: ", rest_url))

  response <- .call_get(rest_url)
  # TODO: check if reponse conains error
  
  message(response)

  tryCatch({response_spdf <- rgdal::readOGR(response, verbose = FALSE, layer = "OGRGeoJSON")},
            warning = function(w) {msg(w, "WARNING")},
            error = function(e) {msg(e, "ERROR")})

  if(isTRUE(export)) {
    # TODO: Error handling in export
    out_dir <- ""
    if(isFALSE(getOption("esriOpendata.out_dir_set"))) {
      msg("No output directory set. Working directory will be selected.")
      out_dir <- getwd()
    } else {
      out_dir <- getOption("esriOpenData.out_dir")
    }
    dsn <- gsub(":", "", slug)
    dsn <- gsub("-", "_", dsn)
    os <- .get_OS()
    if(format == "shp") {
      if (os != "windows") {
        rgdal::writeOGR(response_spdf, paste0(out_dir, "/", dsn, ".shp"), 1, driver = "ESRI Shapefile")
      } else {
        rgdal::writeOGR(response_spdf, paste0(out_dir, "\\", dsn, ".shp"), 1, driver = "ESRI Shapefile")
      }
    }
    if(format == "csv") {
      if (os != "windows") {
        write.csv(response_spdf, paste0(out_dir, "/", dsn, ".csv"))
      } else {
        write.csv(response_spdf, paste0(out_dir, "\\", dsn, ".csv"))
      }
    }
  }

  return(response_spdf)
}