identify.formula: 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(x, data = NULL, ...)

Arguments

A formula of the form y ~ x.

data

The data frame from which the formula should be evaluated.

...

Other arguments to be passed to identify.

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).

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.

Examples

Run this code

## Copy and try in an interactive R session

df <- data.frame(x=runif(10), y=runif(10), grp=factor(rep(c("Yes","No"), each=5)))
plot(y ~ x, data=df)
identify(y ~ x, data=df)