Polygons from a reference map.

Usage

geom_map(mapping = NULL, data = NULL, map, stat = "identity", ...)

Arguments

map
Data frame that contains the map coordinates. This will typically be created using fortify on a spatial object. It must contain columns x or long, y or lat, and region or id.
mapping
The aesthetic mapping, usually constructed with aes or aes_string. Only needs to be set at the layer level if you are overriding the plot defaults.
data
A layer specific dataset - only needed if you want to override the plot defaults.
stat
The statistical transformation to use on the data for this layer.
...
other arguments passed on to layer. This can include aesthetics whose values you want to set, not map. See layer for more details.

Description

Does not affect position scales.

Aesthetics

geom_map understands the following aesthetics (required aesthetics are in bold):

  • map_id
  • alpha
  • colour
  • fill
  • linetype
  • size

Examples

# When using geom_polygon, you will typically need two data frames: # one contains the coordinates of each polygon (positions), and the # other the values associated with each polygon (values). An id # variable links the two together ids <- factor(c("1.1", "2.1", "1.2", "2.2", "1.3", "2.3")) values <- data.frame( id = ids, value = c(3, 3.1, 3.1, 3.2, 3.15, 3.5) ) positions <- data.frame( id = rep(ids, each = 4), x = c(2, 1, 1.1, 2.2, 1, 0, 0.3, 1.1, 2.2, 1.1, 1.2, 2.5, 1.1, 0.3, 0.5, 1.2, 2.5, 1.2, 1.3, 2.7, 1.2, 0.5, 0.6, 1.3), y = c(-0.5, 0, 1, 0.5, 0, 0.5, 1.5, 1, 0.5, 1, 2.1, 1.7, 1, 1.5, 2.2, 2.1, 1.7, 2.1, 3.2, 2.8, 2.1, 2.2, 3.3, 3.2) ) ggplot(values) + geom_map(aes(map_id = id), map = positions) + expand_limits(positions)

ggplot(values, aes(fill = value)) + geom_map(aes(map_id = id), map = positions) + expand_limits(positions)

ggplot(values, aes(fill = value)) + geom_map(aes(map_id = id), map = positions) + expand_limits(positions) + ylim(0, 3)

# Better example crimes <- data.frame(state = tolower(rownames(USArrests)), USArrests) library(reshape2) # for melt crimesm <- melt(crimes, id = 1) if (require(maps)) { states_map <- map_data("state") ggplot(crimes, aes(map_id = state)) + geom_map(aes(fill = Murder), map = states_map) + expand_limits(x = states_map$long, y = states_map$lat) last_plot() + coord_map() ggplot(crimesm, aes(map_id = state)) + geom_map(aes(fill = value), map = states_map) + expand_limits(x = states_map$long, y = states_map$lat) + facet_wrap( ~ variable) }