This is the Lansing Woods Tree data set and an arbitrary polygon boundary
within unit square.
Arguments
Format
lansing is an Rdata.frame with x, y, marks
and polyb is an R matrix with x, y.
References
Gerrard, D.J. (1969) Competition quotient: a new measure of the competition
affecting individual forest trees. Research Bulletin 20,
Agricultural Experiment Station, Michigan State University.