# R/locations.R In ropenaq: Accesses Air Quality Data from the Open Data Platform OpenAQ

#### Documented in aq_locations

#' Providing data about distinct measurement locations.
#'
#' @importFrom lubridate ymd ymd_hms
#' @importFrom dplyr  "%>%" tbl_df rename_
#'
#' @param country Limit results by a certain country -- a two-letters code see countries() for finding code based on name.
#' @param city Limit results by a certain city.
#' @param location Limit results by a certain location.
#' @param parameter Limit to only a certain parameter (valid values are 'pm25', 'pm10', 'so2', 'no2', 'o3', 'co' and 'bc').
#' If no parameter is given, all parameters are retrieved.
#' @param has_geo has_geo Filter out items that have or do not have geographic information.
#' @param latitude Latitude of the center point (lat, lon) used to get measurements within a certain area.
#' @param longitude Longitude of the center point (lat, lon) used to get measurements within a certain area.
#' @param radius Radius (in meters) used to get measurements within a certain area, must be used with latitude and longitude
#' @param limit Change the number of results returned, max is 10000.
#' @param page The page of the results to query. This can be useful if e.g. there are 2000 measurements, then first use page=1 and page=2 with limit=100 to get all measurements for your query.

#' @return  A results data.frame (dplyr "tbl_df") with 12 columns:
#'  \itemize{
#'  \item the name of the location ("location"),
#'  \item the city it is in ("city"),
#'  \item the code of country it is in ("country"),
#'  \item the name of the source of the information ("sourceName"),
#'  \item the number of measures for this location in the platform ("count"),
#'  \item the last time and date at which measures were updated for this location ("lastUpdated"),
#'  \item the first time and date at which measures were updated for this location ("firstUpdated"),
#'  \item the parameters available for this location ("parameters"),
#'  \item its longitude ("longitude") and latitude if available ("latitude"),
#'  \item and finally an URL encoded version of the city name ("cityURL")
#'  \item and of the location name ("locationURL").
#'  }
#' and two attributes, a meta data.frame (dplyr "tbl_df") with 1 line and 5 columns:
#' \itemize{
#' \item the API name ("name"),
#' \item the license of the data ("license"),
#' \item the website url ("website"),
#' \item the queried page ("page"),
#' \item the limit on the number of results ("limit"),
#' \item the number of results found on the platform for the query ("found")
#' }
#' and a timestamp data.frame (dplyr "tbl_df") with the query time and the last time at which the data was modified on the platform.
#' @details For queries involving a city or location argument,
#' the URL-encoded name of the city/location (as in cityURL/locationURL),
#' not its name, should be used.
#'  You can query any nested combination of country/location/city (level 1, 2 and 3),
#'  with only one value for each argument.
#'   If you write inconsistent combination such as city="Paris" and country="IN", an error message will be returned.
#'   If you write city="Delhi", you do not need to write the code of the country, unless
#'   one day there is a city with the same name in another country.
#' @export
#'
#' @examples
#' \dontrun{
#' aq_locations(city='Delhi', parameter='co')
#' }
aq_locations <- function(country = NULL, city = NULL, location = NULL,# nolint
parameter = NULL, has_geo = NULL, limit = 10000,
latitude = NULL, longitude = NULL, radius = NULL,
page = NULL) {

####################################################
# BUILD QUERY base URL
urlAQ <- paste0(base_url(), "locations")

argsList <- buildQuery(country = country, city = city,
location = location,
parameter = parameter,
has_geo = has_geo,
limit = limit,
latitude = latitude,
longitude = longitude,
page = page)

####################################################
# GET AND TRANSFORM RESULTS
output <- getResults(urlAQ, argsList)
locationsTable <- output
if (nrow(locationsTable) != 0){

locationsTable <- functionParameters(resTable =
locationsTable)

locationsTable <- addCityURL(resTable =
locationsTable)
locationsTable <- addLocationURL(resTable =
locationsTable)

locationsTable <- functionTime(resTable =
locationsTable,
"firstUpdated")
locationsTable <- functionTime(resTable = locationsTable,
"lastUpdated")

names(locationsTable) <- gsub("coordinates\\.",
"",
names(locationsTable))
}
####################################################
# DONE!
attr(locationsTable, "meta") <- attr(output, "meta")
attr(locationsTable, "timestamp") <- attr(output, "timestamp")

return(locationsTable)

}


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ropenaq documentation built on May 2, 2019, 3:26 a.m.