Reads the position of the graphics cursor when the (first) mouse button is pressed.
locator(n = 512, type = "n", …)the maximum number of points to locate. Valid values start at 1.
One of "n", "p", "l" or
"o". If "p" or "o" the points are
plotted; if "l" or "o" they are joined by lines.
additional graphics parameters used if type != "n"
for plotting the locations.
A list containing x and y components which are the
coordinates of the identified points in the user coordinate system,
i.e., the one specified by par("usr").
locator is only supported on screen devices such as
X11, windows and quartz. On other devices the
call will do nothing.
Unless the process is terminated prematurely by the user (see below)
at most n positions are determined.
For the usual X11 device the identification process is
terminated by pressing any mouse button other than the first.
For the quartz device the process is terminated by
pressing the ESC key.
The identification process can be terminated by clicking the second
button and selecting ‘Stop’ from the menu, or from the
‘Stop’ menu on the graphics window.
The current graphics parameters apply just as if plot.default
has been called with the same value of type. The plotting of
the points and lines is subject to clipping, but locations outside the
current clipping rectangle will be returned.
On most devices which support locator, successful selection of
a point is indicated by a bell sound unless
options(locatorBell = FALSE) has been set.
If the window is resized or hidden and then exposed before the input
process has terminated, any lines or points drawn by locator
will disappear. These will reappear once the input process has
terminated and the window is resized or hidden and exposed again.
This is because the points and lines drawn by locator are not
recorded in the device's display list until the input process has
terminated.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
dev.capabilities to see if it is supported.