R: Create a layer of map borders

borders {ggplot2}

R Documentation

Create a layer of map borders

Description

This is a quick and dirty way to get map data (from the maps package) on to your plot. This is a good place to start if you need some crude reference lines, but you'll typically want something more sophisticated for communication graphics.

Usage

borders(database = "world", regions = ".", fill = NA, colour = "grey50",
  xlim = NULL, ylim = NULL, ...)

Arguments

`database`	map data, see `maps::map()` for details
`regions`	map region
`fill`	fill colour
`colour`	border colour
`xlim, ylim`	latitudinal and logitudinal range for extracting map polygons, see `maps::map()` for details.
`...`	Arguments passed on to `geom_polygon` mapping Set of aesthetic mappings created by `aes()` or `aes_()`. If specified and `inherit.aes = TRUE` (the default), it is combined with the default mapping at the top level of the plot. You must supply `mapping` if there is no plot mapping. data The data to be displayed in this layer. There are three options: If `NULL`, the default, the data is inherited from the plot data as specified in the call to `ggplot()`. A `data.frame`, or other object, will override the plot data. All objects will be fortified to produce a data frame. See `fortify()` for which variables will be created. A `function` will be called with a single argument, the plot data. The return value must be a `data.frame.`, and will be used as the layer data. stat The statistical transformation to use on the data for this layer, as a string. position Position adjustment, either as a string, or the result of a call to a position adjustment function. show.legend logical. Should this layer be included in the legends? `NA`, the default, includes if any aesthetics are mapped. `FALSE` never includes, and `TRUE` always includes. It can also be a named logical vector to finely select the aesthetics to display. inherit.aes If `FALSE`, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. `borders()`. na.rm If `FALSE`, the default, missing values are removed with a warning. If `TRUE`, missing values are silently removed.

Examples

if (require("maps")) {

ia <- map_data("county", "iowa")
mid_range <- function(x) mean(range(x))
seats <- plyr::ddply(ia, "subregion", plyr::colwise(mid_range, c("lat", "long")))
ggplot(ia, aes(long, lat)) +
  geom_polygon(aes(group = group), fill = NA, colour = "grey60") +
  geom_text(aes(label = subregion), data = seats, size = 2, angle = 45)

data(us.cities)
capitals <- subset(us.cities, capital == 2)
ggplot(capitals, aes(long, lat)) +
  borders("state") +
  geom_point(aes(size = pop)) +
  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()
}

[Package ggplot2 version 3.0.0 Index]