| identify {graphics} | R Documentation |
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.
identify(x, ...)
## Default S3 method:
identify(x, y = NULL, labels = seq(along = x), pos = FALSE,
n = length(x), plot = TRUE, atpen = FALSE, offset = 0.5,
tolerance = 0.25, ...)
x,y |
coordinates of points in a scatter plot. Alternatively, any
object which defines coordinates (a plotting structure, time
series etc: see xy.coords) 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: see Value. |
n |
the maximum number of points to be identified. |
plot |
logical: if plot is TRUE, the labels are printed at
the points and if FALSE they are omitted. |
atpen |
logical: if TRUE and plot = TRUE, the
lower-left corners of the labels are plotted at the points clicked
rather than relative to the points. |
offset |
the distance (in character widths) which separates the
label from identified points. Ignored if atpen = TRUE or
pos = 0. |
tolerance |
the maximal distance (in inches) for the pointer to be ‘close enough’ to a point. |
... |
further arguments passed to par such as
cex, col and font. |
identify is only supported on screen devices such as
X11, windows and quartz. On other devices the
call will do nothing.
If plot is TRUE, the point is labelled with
the corresponding element of text.
The labels are placed below, to the left, above or to the right
of the identified point, depending on where the cursor was relative to
the point.
For the usual X11 device the identification process is
terminated by pressing any mouse button other than the first.
For the quartz device the process is terminated by
pressing the ESC key.
On most devices which support identify, 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 identification
process has terminated, any labels drawn by 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 identify are not
recorded in the device's display list until the identification process has
terminated.
If pos is FALSE, an integer
vector containing the indexes of the identified points.
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).
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.