Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

99 lines (95 sloc) 3.553 kb
#' Fortify method for map objects.
#'
#' This function turns a map into a data frame that can more easily be
#' plotted with ggplot2.
#'
#' @export
#' @seealso \code{\link{map_data}} and \code{\link{borders}}
#' @param model map object
#' @param data not used by this method
#' @param ... not used by this method
#' @examples
#' if (require("maps")) {
#' ca <- map("county", "ca", plot = FALSE, fill = TRUE)
#' head(fortify(ca))
#' qplot(long, lat, data = ca, geom = "polygon", group = group)
#'
#' tx <- map("county", "texas", plot = FALSE, fill = TRUE)
#' head(fortify(tx))
#' qplot(long, lat, data = tx, geom = "polygon", group = group,
#' colour = I("white"))
#' }
fortify.map <- function(model, data, ...) {
df <- as.data.frame(model[c("x", "y")])
names(df) <- c("long", "lat")
df$group <- cumsum(is.na(df$long) & is.na(df$lat)) + 1
df$order <- 1:nrow(df)
names <- do.call("rbind", lapply(strsplit(model$names, "[:,]"), "[", 1:2))
df$region <- names[df$group, 1]
df$subregion <- names[df$group, 2]
df[complete.cases(df$lat, df$long), ]
}
#' Create a data frame of map data.
#'
#' @param map name of map provided by the \pkg{maps} package. These
#' include \code{\link[maps]{county}}, \code{\link[maps]{france}},
#' \code{\link[maps]{italy}}, \code{\link[maps]{nz}},
#' \code{\link[maps]{state}}, \code{\link[maps]{usa}},
#' \code{\link[maps]{world}}, \code{\link[maps]{world2}}.
#' @param region name of subregions to include. Defaults to \code{.} which
#' includes all subregion. See documentation for \code{\link[maps]{map}}
#' for more details.
#' @param exact should the \code{region} be treated as a regular expression
#' (\code{FALSE}) or as a fixed string (\code{TRUE}).
#' @param ... all other arguments passed on to \code{\link[maps]{map}}
#' @export
#' @examples
#' if (require("maps")) {
#' states <- map_data("state")
#' arrests <- USArrests
#' names(arrests) <- tolower(names(arrests))
#' arrests$region <- tolower(rownames(USArrests))
#'
#' choro <- merge(states, arrests, sort = FALSE, by = "region")
#' choro <- choro[order(choro$order), ]
#' qplot(long, lat, data = choro, group = group, fill = assault,
#' geom = "polygon")
#' qplot(long, lat, data = choro, group = group, fill = assault / murder,
#' geom = "polygon")
#' }
map_data <- function(map, region = ".", exact = FALSE, ...) {
try_require("maps")
fortify(map(map, region, exact = exact, plot = FALSE, fill = TRUE, ...))
}
#' Create a layer of map borders.
#'
#' @param database map data, see \code{\link[maps]{map}} for details
#' @param regions map region
#' @param fill fill colour
#' @param colour border colour
#' @param ... other arguments passed onto \code{\link{geom_polygon}}
#' @export
#' @examples
#' if (require("maps")) {
#'
#' ia <- map_data("county", "iowa")
#' mid_range <- function(x) mean(range(x))
#' library(plyr)
#' seats <- ddply(ia, .(subregion), colwise(mid_range, .(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()
#'
#' }
borders <- function(database = "world", regions = ".", fill = NA, colour = "grey50", ...) {
df <- map_data(database, regions)
geom_polygon(aes_q(quote(long), quote(lat), group = quote(group)), data = df,
fill = fill, colour = colour, ...)
}
Jump to Line
Something went wrong with that request. Please try again.