cluster.overplot: Shift overlying points into clusters.
Description
cluster.overplot checks for overlying points in the x and y
coordinates passed. Those points that are overlying are moved to form
a small cluster of up to nine points. For large numbers of overlying
points, see count.overplot or sizeplot.
Usage
cluster.overplot(x,y,away=NULL,tol=NULL)
Arguments
x,y
Numeric data vectors or the first two columns of a matrix
or data frame. Typically the x/y coordinates of points to be plotted.
away
How far to move overlying points in user units. Defaults to
the width of a lower case "o" in the x direction and 5/8 of the
height of a lower case "o" in the y direction.
tol
The largest distance between points that will be considered
to be overlying. Defaults to 1/2 of the width of a lower case "o" in
the x direction and 1/2 of the height of a lower case "o" in the y
direction.
Value
A list with two components. For unique x-y pairs the elements will be
the same as in the original. For overlying points up to eight additional
points will be generated that will create a cluster of points instead of one.