If a line segment pattern is plotted in the graphics window, this function will find the segment which is nearest to the mouse position, and print its serial number.
# S3 method for psp
identify(x, …, labels=seq_len(nsegments(x)), n=nsegments(x), plot=TRUE)A line segment pattern (object of class "psp").
Labels associated with the segments, to be plotted when the
segments are identified. A character vector or numeric vector
of length equal to the number of segments in x.
Maximum number of segments to be identified.
Logical. Whether to plot the labels when a segment is identified.
Arguments passed to text.default
controlling the plotting of the labels.
Vector containing the serial numbers of the segments in the pattern
x that were identified.
This is a method for the generic function identify
for line segment pattern objects.
The line segment pattern x should first be plotted
using plot.psp. Then identify(x)
reads the position of the graphics pointer each time the
left mouse button is pressed. It then finds
the segment in the pattern x that is closest to the mouse position.
This segment's index will be returned as part of the value of the call.
Each time a segment is identified,
text will be displayed next to the point,
showing its serial number (or the relevant entry of labels).