\Header{identify}{Identify Points in a Scatter Plot}
\methalias{identify.default}{identify}
\keyword{iplot}{identify}
\begin{Description}\relax
\code{identify} reads the position of the graphics pointer when the
(first) mouse button is pressed.  It then searches the coordinates
given in \code{x} and \code{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.\end{Description}
\begin{Usage}
\begin{verbatim}
identify(x, ...)
identify.default(x, y = NULL, labels = seq(along = x), pos = FALSE,
                 n = length(x), plot = TRUE, offset = 0.5, ...)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{x,y}] coordinates of points in a scatter plot.  Alternatively, any
object which defines coordinates (a plotting structure, time
series etc.) can be given as \code{x} and \code{y} left undefined.
\item[\code{labels}] an optional vector, the same length as \code{x} and
\code{y}, giving labels for the points.
\item[\code{pos}] if \code{pos} is \code{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).
\item[\code{n}] the maximum number of points to be identified.
\item[\code{plot}] if \code{plot} is \code{TRUE}, the labels are printed at
the points and if \code{FALSE} they are omitted.
\item[\code{offset}] the distance (in character widths) which separates the
label from identified points.
\item[\code{...}] further arguments to \code{par(.)}.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
If in addition, \code{plot} is \code{TRUE}, the point is labelled with
the corresponding element of \code{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.

If the window is resized or hidden and then exposed before the identification
process has terminated, any labels drawn by \code{identify}
will disappear.  These will reappear once the identification process has 
terminated and the window is resized or hidden and exposed again.
This is because the labels drawn by \code{identify} are not
recorded in the device's display list until the identification process has
terminated.\end{Details}
\begin{Value}
If \code{pos} is \code{FALSE}, an integer
vector containing the indexes of the identified points.

If \code{pos} is \code{TRUE}, a list containing a component
\code{ind}, indicating which points were identified and a component
\code{pos}, indicating where the labels were placed relative to the
identified points.\end{Value}
\begin{SeeAlso}\relax
\code{\Link{locator}}\end{SeeAlso}

