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.

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.

### 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`

[Package graphics version 2.3.1 Index]