R/geojson_sf.R

In geojsonio: Convert Data from and to 'GeoJSON' or 'TopoJSON'

#' Convert objects to an sf class
#'
#' @export
#' @param x Object of class `geo_list`, `geo_json`, string, or json
#' @param stringsAsFactors Convert strings to Factors? Default `FALSE`.
#' @param ... Further args passed on to [sf::st_read()]
#'
#' @return An sf class object, see Details.
#' @details The type of sf object returned will depend on the input GeoJSON.
#' Sometimes you will get back a `POINTS` class, and sometimes a
#' `POLYGON` class, etc., depending on what the structure of the GeoJSON.
#'
#' The reading and writing of the CRS to/from geojson is inconsistent. You can
#' directly set the CRS by passing a valid PROJ4 string or epsg code to the crs
#' argument in [sf::st_read()]
#'
#' @examples \dontrun{
#' library(sf)
#'
#' # geo_list ------------------
#' ## From a numeric vector of length 2 to a point
#' vec <- c(-99.74, 32.45)
#' geojson_list(vec) %>% geojson_sf()
#'
#' ## Lists
#' ## From a list
#' mylist <- list(
#'   list(latitude = 30, longitude = 120, marker = "red"),
#'   list(latitude = 30, longitude = 130, marker = "blue")
#' )
#' geojson_list(mylist) %>% geojson_sf()
#' geojson_list(mylist) %>%
#'   geojson_sf() %>%
#'   plot()
#'
#' ## From a list of numeric vectors to a polygon
#' vecs <- list(c(100.0, 0.0), c(101.0, 0.0), c(101.0, 1.0), c(100.0, 1.0), c(100.0, 0.0))
#' geojson_list(vecs, geometry = "polygon") %>% geojson_sf()
#' geojson_list(vecs, geometry = "polygon") %>%
#'   geojson_sf() %>%
#'   plot()
#'
#' # geo_json ------------------
#' ## from point
#' geojson_json(c(-99.74, 32.45)) %>% geojson_sf()
#' geojson_json(c(-99.74, 32.45)) %>%
#'   geojson_sf() %>%
#'   plot()
#'
#' # from featurecollectino of points
#' geojson_json(us_cities[1:2, ], lat = "lat", lon = "long") %>% geojson_sf()
#' geojson_json(us_cities[1:2, ], lat = "lat", lon = "long") %>%
#'   geojson_sf() %>%
#'   plot()
#'
#' # Set the CRS via the crs argument
#' geojson_json(us_cities[1:2, ], lat = "lat", lon = "long") %>% geojson_sf(crs = "+init=epsg:4326")
#'
#' # json ----------------------
#' x <- geojson_json(us_cities[1:2, ], lat = "lat", lon = "long")
#' geojson_sf(x)
#'
#' # character string ----------------------
#' x <- unclass(geojson_json(c(-99.74, 32.45)))
#' geojson_sf(x)
#' }
geojson_sf <- function(x, stringsAsFactors = FALSE, ...) {
  UseMethod("geojson_sf")
}

#' @export
geojson_sf.character <- function(x, stringsAsFactors = FALSE, ...) {
  tosf(as.json(x), stringsAsFactors = stringsAsFactors, ...)
}

#' @export
geojson_sf.geo_list <- function(x, stringsAsFactors = FALSE, ...) {
  tosf(as.json(x), stringsAsFactors = stringsAsFactors, ...)
}

#' @export
geojson_sf.geo_json <- function(x, stringsAsFactors = FALSE, ...) {
  tosf(x, stringsAsFactors = stringsAsFactors, ...)
}

#' @export
geojson_sf.json <- function(x, stringsAsFactors = FALSE, ...) {
  tosf(x, stringsAsFactors = stringsAsFactors, ...)
}

tosf <- function(x, stringsAsFactors, ...) {
  sf::st_read(unclass(x), quiet = TRUE, stringsAsFactors = stringsAsFactors, ...)
}