The data record the locations and diameters of 
  584 Longleaf pine (Pinus palustris) trees 
  in a 200 x 200 metre region in southern Georgia (USA).
  They were collected and analysed by Platt, Evans and Rathbun (1988).
 
  This is a marked point pattern; the mark associated with a tree is its
  diameter at breast height (dbh), a convenient measure of its size. 
  Several analyses have considered only the ``adult'' trees which
  are conventionally defined as those trees with dbh
  greater than or equal to 30 cm.
 
  The pattern is regarded as spatially inhomogeneous.
data(longleaf)"ppp"
  representing the point pattern of tree locations.
  Entries include
  x 	Cartesian $x$-coordinate of tree 
y 	Cartesian $y$-coordinate of tree 
marks 	diameter at breast height, in centimetres.
  }
  See ppp.object for details of the format of a
  point pattern object.Rathbun, S. L. and Cressie, N. (1994) A space-time survival point process for a longleaf pine forest in southern Georgia. Journal of the American Statistical Association 89, 1164--1173.