gglocator: Locator for ggplots.
In fresques/ggmap: Spatial Visualization with ggplot2

Description Usage Arguments Value Author(s) Examples

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

1 2	gglocator(n = 1, message = FALSE, xexpand = c(0, 0), yexpand = c(0, 0), mercator = TRUE)

`n`	number of points to locate.
`message`	unused
`xexpand`	expand argument in scale_x_continuous
`yexpand`	expand argument in scale_y_continuous
`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.

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

Tyler Rinker with help from Baptiste Auguie and StackOverflow user DWin with additions and canning by David Kahle david.kahle@gmail.com. Updated by \@Nikolai-Hlubek and \@mvkorpel.

if(interactive()){

# only run for interactive sessions
df <- expand.grid(x = 0:-5, y = 0:-5)
p <- qplot(x, y, data = df) +
  annotate(geom = "point", x = -2, y = -2, colour = "red")
print(p)
cat("click red point\n")
print(pt <- gglocator(mercator = FALSE))
p2 <- last_plot() +
  annotate("point", pt$x, pt$y, color = "blue", size = 3, alpha = .5)
cat("a blue point should appear where you clicked\n")
print(p2)

p3 <- p +
  scale_x_continuous(expand = c(0,0)) +
  scale_y_continuous(expand = c(0,0))
print(p3)
cat("click any point\n")
print(gglocator(1, xexpand = c(0,0), yexpand = c(0,0),
                mercator = FALSE))


}