Merge branch 'markpayneatwork-master'

Author: hadley

NEWS.md

@@ -351,6 +351,9 @@ version of ggplot.
   making it easier to plot multiple grobs with the same name (e.g. grobs of
   ggplot2 graphics) in the same plot (#1256).
 
+* `borders()` now accepts xlim and ylim arguments for specifying the geographical 
+  region of interest (@markpayneatwork, #1392).
+
 * `coord_cartesian()` applies the same expansion factor to limits as for scales. 
   You can suppress with `expand = FALSE` (#1207).
 

R/fortify-map.r

@@ -74,6 +74,8 @@ map_data <- function(map, region = ".", exact = FALSE, ...) {
 #' @param regions map region
 #' @param fill fill colour
 #' @param colour border colour
+#' @param xlim,ylim latitudinal and logitudinal range for extracting map
+#'   polygons, see \code{\link[maps]{map}} for details.
 #' @param ... other arguments passed onto \code{\link{geom_polygon}}
 #' @export
 #' @examples
@@ -91,11 +93,19 @@ map_data <- function(map, region = ".", exact = FALSE, ...) {
 #' ggplot(capitals, aes(long, lat)) +
 #'   borders("state") +
 #'   geom_point(aes(size = pop)) +
-#'   scale_size_area()
+#'   scale_size_area() +
+#'   coord_quickmap()
 #'
+#' # Same map, with some world context
+#' ggplot(capitals, aes(long, lat)) +
+#'   borders("world", xlim = c(-130, -60), ylim = c(20, 50)) +
+#'   geom_point(aes(size = pop)) +
+#'   scale_size_area() +
+#'   coord_quickmap()
 #' }
-borders <- function(database = "world", regions = ".", fill = NA, colour = "grey50", ...) {
-  df <- map_data(database, regions)
+borders <- function(database = "world", regions = ".", fill = NA,
+                    colour = "grey50", xlim = NULL, ylim = NULL, ...) {
+  df <- map_data(database, regions, xlim = xlim, ylim = ylim)
   geom_polygon(aes_(~long, ~lat, group = ~group), data = df,
     fill = fill, colour = colour, ..., inherit.aes = FALSE)
 }