ggsn (version 0.3.1)

scalebar: Scale bar

Description

Adds a scale bar to maps created with ggplot or ggmap.

Usage

scalebar(data = NULL, location = "bottomright", dist, height = 0.02, st.dist = 0.02, st.bottom = TRUE, st.size = 5, dd2km = NULL, model, x.min, x.max, y.min, y.max, anchor = NULL, facet.var = NULL, facet.lev = NULL)

Arguments

data

the same data.frame passed to ggplot to plot the map.

location

string indicating the symbol's location in the plot. Possible options: "topright" (default), "bottomright", "bottomleft" and "topleft".

dist

distance in km to represent with each segment of the scale bar.

height

number between 0 and 1 to indicate the height of the scale bar, as a proportion of the y axis.

st.dist

number between 0 and 1 to indicate the distance between the scale bar and the scale bar text, as a proportion of the y axis.

st.bottom

logical. If TRUE (default) the scale bar text is displayed at the bottom of the scale bar, if FALSE, it is displayed at the top.

st.size

number to indicate the scale bar text size. It is passed to the size argument of annotate function.

dd2km

logical. If TRUE dist it is assumed that map coordinates are in decimal degrees, if FALSE, it assumed they are in meters.

model

choice of ellipsoid model ("WGS84", "GRS80", "Airy", "International", "Clarke", "GRS67") Used when dd2km is TRUE.

x.min

if data is not defined, number with the minimum x coordinate. Useful for ggmap.

x.max

if data is not defined, number with the maximum x coordinate. Useful for ggmap.

y.min

if data is not defined, number with the minimum y coordinate. Useful for ggmap.

y.max

if data is not defined, number with the maximum y coordinate. Useful for ggmap.

anchor

named vector with coordinates to control the symbol position. For location = "topright", anchor defines the coordinates of the symbol's topright corner and so forth. The x coordinate must be named as x and the y coordinate as y.

facet.var

if faceting, variable name used for faceting. This is useful for placing the scalebar only in one facet and must be used together with facet.lev.

facet.lev

one of the level names in facet.var. The scale bar will be drawn only in the facet.lev facet.

Examples

library(rgdal); library(broom)
dsn <- system.file('extdata', package = 'ggsn')
## Map in geographic coordinates.
map <- readOGR(dsn, 'sp')
map@data$id <- 1:nrow(map@data)
map.df <- merge(tidy(map), map, by = 'id')

ggplot(data = map.df, aes(long, lat, group = group, fill = nots)) +
    geom_polygon() +
    coord_equal() +
    geom_path() +
    scale_fill_brewer(name = 'Animal abuse\nnotifications', palette = 8) +
    scalebar(map.df, dist = 5, dd2km = TRUE, model = 'WGS84')