grid.locator {grid} | R Documentation |
Allows the user to click the mouse once within the current graphics device and returns the location of the mouse click within the current viewport, in the specified coordinate system.
grid.locator(unit = "native")
unit |
The coordinate system in which to return the location
of the mouse click.
See the unit function for valid coordinate systems. |
This function is modal (like the base function locator
) so
the command line and graphics drawing is blocked until
the use has clicked the mouse in the current device.
A unit object representing the location of the mouse click within the
current viewport, in the specified coordinate system.
If the user did not click mouse button 1, the function
(invisibly) returns NULL
.
Paul Murrell
if (interactive()) { ## Need to write a more sophisticated unit as.character method unittrim <- function(unit) { sub("^([0-9]+|[0-9]+[.][0-9])[0-9]*", "\\1", as.character(unit)) } do.click <- function(unit) { click.locn <- grid.locator(unit) grid.segments(unit.c(click.locn$x, unit(0, "npc")), unit.c(unit(0, "npc"), click.locn$y), click.locn$x, click.locn$y, gp=gpar(lty="dashed", col="grey")) grid.points(click.locn$x, click.locn$y, pch=16, size=unit(1, "mm")) clickx <- unittrim(click.locn$x) clicky <- unittrim(click.locn$y) grid.text(paste("(", clickx, ", ", clicky, ")", sep=""), click.locn$x + unit(2, "mm"), click.locn$y, just="left") } do.click("inches") pushViewport(viewport(width=0.5, height=0.5, xscale=c(0, 100), yscale=c(0, 10))) grid.rect() grid.xaxis() grid.yaxis() do.click("native") popViewport() }