## Identify Points in a Scatter Plot

## Usage

    identify(x, y = NULL, labels = seq(along = x), pos = FALSE,
             n = length(x), plot = TRUE, offset = 0.5, ...)

## Arguments

`x,y` | coodinates of points in a scatter plot. Alternatively, any object which can defines coordinates (a plotting structure, time series etc.) can be given as `x` and `y` left undefined.
`labels` | an optional vector, the same length as `x` and `y`, giving labels for the points.
`pos` | if `pos` is `TRUE`, a component is added to the return value which indicates where text was plotted relative to each identified point (1=below, 2=left, 3=above and 4=right).
`n` | the maximum number of points to be identified. (Not yet implemented.)
`plot` | if `plot` is `TRUE`, the labels are printed at the points and if `FALSE` they are omitted. (Not yet implemented.)
`offset` | the distance (in character widths) which separates the label from identified points. (Not yet implemented.)
`...` | further arguments to `par(.)`.

## Description

This function reads the position of the graphics pointer when the (first) mouse button is pressed. It then searches the coordinates given in `x` and `y` for the point closest to the pointer. If this point is close to the pointer, its index will be returned as part of the value of the call.

The following, and the `n`, `ploy` and `offset` arguments are not yet implented: If in addition, `plot` is `TRUE` the point is labelled with the corresponding element of `text`.

The labels are placed either below, to the left, above or to the right of the identified point, depending on where the cursor was.

The identification process is terminated by pressing any mouse button other than the first, or by clicking outside the graphics window.

## Value

If `pos` is `FALSE`, `identify` returns an integer vector containing the indexes of the identified points. If `pos` is `TRUE`, `identify` returns a list containing a component `ind`, indicating which points were an identified and a component `pos`, indicating where the labels were placed relative to the identified points.

[Package Contents]