locator {graphics}R Documentation

Graphical Input

Description

Reads the position of the graphics cursor when the (first) mouse button is pressed.

Usage

locator(n = 512, type = "n", ...)

Arguments

n

the maximum number of points to locate. Valid values start at 1.

type

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.

Details

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 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.

Value

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").

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

identify.

dev.capabilities to see if it is supported.


[Package graphics version 3.0.0 Index]