Webmercator fix

DESCRIPTION

@@ -35,9 +35,10 @@ Imports:
 Suggests:
     MASS,
     hexbin,
-    testthat
+    testthat,
+    sf
 License: GPL-2
 LazyData: true
-RoxygenNote: 7.1.0
+RoxygenNote: 7.1.2
 Roxygen: list(markdown = TRUE)
 Encoding: UTF-8

NAMESPACE

@@ -28,6 +28,7 @@ export(ggmap)
 export(ggmap_credentials)
 export(ggmap_hide_api_key)
 export(ggmap_show_api_key)
+export(ggmap_to_webmercator)
 export(ggmapplot)
 export(google_account)
 export(google_client)
@@ -120,6 +121,7 @@ importFrom(purrr,walk)
 importFrom(rlang,set_names)
 importFrom(scales,expand_range)
 importFrom(stats,asOneSidedFormula)
+importFrom(stats,setNames)
 importFrom(stats,time)
 importFrom(stringr,str_c)
 importFrom(stringr,str_detect)

R/ggmap_to_webmercator.R

@@ -0,0 +1,30 @@
+#' \code{ggmap_to_webmercator} change bounding box to match with sf objects (CRS needs to be 3857)
+#'
+#' @param map The map to update
+
+#' @export
+#' @rdname ggmap_to_webmercator
+#' @importFrom stats setNames
+#'
+ggmap_to_webmercator <- function(map) {
+  if (!inherits(map, "ggmap")) stop("map must be a ggmap object")
+  # Extract the bounding box (in lat/lon) from the ggmap to a numeric vector,
+  # and set the names to what sf::st_bbox expects:
+  map_bbox <- setNames(unlist(attr(map, "bb")),
+                       c("ymin", "xmin", "ymax", "xmax"))
+
+  # Coonvert the bbox to an sf polygon, transform it to 3857,
+  # and convert back to a bbox (convoluted, but it works)
+  if( !requireNamespace("sf") )
+    stop("package sf is required to use this function")
+
+  bbox_3857 <- sf::st_bbox(sf::st_transform(sf::st_as_sfc(sf::st_bbox(map_bbox, crs = 4326)), 3857))
+
+  # Overwrite the bbox of the ggmap object with the transformed coordinates
+  attr(map, "bb")$ll.lat <- bbox_3857["ymin"]
+  attr(map, "bb")$ll.lon <- bbox_3857["xmin"]
+  attr(map, "bb")$ur.lat <- bbox_3857["ymax"]
+  attr(map, "bb")$ur.lon <- bbox_3857["xmax"]
+
+  map
+}