R/ll_match_geo.R

In giocomai/latlon2map: Facilitates matching lat/lon data with administrative units and other geographic shapes

#' Matches a data frame with longitude and latitude to an sf object
#'
#' @param data A data frame or tibble with a column for longitude and one for latitude or an onject of the sf class. If an sf object is given, the longitude and latitude parameters are ignored.
#' @param longitude The exact column name or the column index (e.g. 1 if first column) for longitude. Defaults to 1.
#' @param latitude The exact column name or the column index (e.g. 1 if first column) for latitude. Defaults to 2.
#' @param join A function of the sf class determining the type of join. Defaults to `sf::st_intersects`. Check `?sf::st_join` for alternatives.
#' @param sample Defaults to NULL. If given, it runs the matching with only a subset of the original dataframe. Suggested for testing in particular when working with big datasets.
#' @param match An sf object to be matched with the given dataframe, defaults to `longlat2map::ll_get_world()`. This package facilitate obtaining alternative reference maps with functions such as `longlat2map::ll_get_nuts_eu()` and `longlat2map::ll_get_nuts_us()`
#'
#' @return An sf object with CRS 4326.
#' @export
#'
#' @examples
ll_match <- function(data,
                     longitude = 1,
                     latitude = 2,
                     join = sf::st_intersects,
                     sample = NULL,
                     match = longlat2map::ll_get_world()) {
  if (is.null(sample) == FALSE) {
    data <- data %>% dplyr::sample_n(size = sample)
  }

  if (is.element("sf", class(data)) == FALSE) {
    sf_data <- data %>%
      sf::st_as_sf(coords = c(longitude, latitude), crs = 4326)
  } else {
    sf_data <- data
  }

  sf::st_join(sf_data %>% sf::st_transform(crs = 4326),
    match %>% sf::st_transform(crs = 4326),
    join = join
  )
}