gglocator function

Locator for ggplot objects

Locator for ggplot objects (Note : only accurate when extent = "normal" when using ggmap.)

gglocator(n = 1, message = FALSE, mercator = TRUE, ...)

Arguments

• n: number of points to locate.
• message: unused
• mercator: logical flag; should the plot be treated as using the projection common to most web map services? Set to FALSE if the axes on the plot use a linear scale.
• ...: additional arguments (including deprecated, e.g. xexpand)

Returns

a data frame with columns according to the x and y aesthetics

Examples

if (interactive()) {

# only run for interactive sessions
df <- expand.grid(x = 0:-5, y = 0:-5)

ggplot(df, aes(x, y)) + geom_point() +
  annotate(geom = "point", x = -2, y = -2, colour = "red")

(pt <- gglocator(mercator = FALSE)) # click red point

last_plot() +
  annotate("point", pt$x, pt$y, color = "blue", size = 3, alpha = .5)

hdf <- get_map("houston, texas")
ggmap(hdf, extent = "normal")
(pt <- gglocator(mercator = TRUE))
last_plot() +
  annotate("point", pt$lon, pt$lat, color = "blue", size = 3, alpha = .5)

}

Author(s)

Tyler Rinker, Baptiste Auguie, DWin, David Kahle, @Nikolai-Hlubek and @mvkorpel.