R: Identify Points In a Plot Using a Formula

identify.formula {DescTools} | R Documentation

## Identify Points In a Plot Using a Formula

### Description

The function `identify` 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 enough to the pointer, its index will be returned as part of the value of the call.

### Usage

      ## S3 method for class 'formula'
     identify(formula, data, subset, na.action, ...)

### Arguments

`formula` | a formula of the form `lhs ~ rhs` where `lhs` gives the data values and rhs the corresponding groups.
`data` | The data frame from which the formula should be evaluated.
`subset` | an optional vector specifying a subset of observations to be used.
`na.action` | a function which indicates what should happen when the data contain NAs. Defaults to `getOption("na.action")`.
`...` | Other arguments to be passed to `identify`.

### Details

This function is meant to make it easier to call `identify` after `plot` has been called using a formula and the `data` argument.

A two dimensional plot must be active and the vectors in `x` and data frame in `data` must correspond to the x- and y-axes and the data of the plot.

### Value

If `pos` is `FALSE`, an integer vector containing the indices of the identified points, in the order they were identified. If `pos` is `TRUE`, a list containing a component `ind`, indicating which points were identified and a component `pos`, indicating where the labels were placed relative to the identified points (1=below, 2=left, 3=above, 4=right and 0=no offset, used if `atpen = TRUE`).

### Author(s)

Derek Ogle <dogle@northland.edu>

### See Also

`identify`, `locator`, `text`
http://www.rforge.net/NCStats/files/

### Examples

    ## Not run:
    ## Copy and try in an interactive R session
    plot(dist ~ speed, data = cars, subset = speed < 17)
    identify(dist ~ speed, data = cars, subset = speed < 17)

    ## End(Not run)

[Package DescTools version 0.99.38 Index]