It is possible to build a spatially structured randomisation, where labels
are assigned randomly to groups based on spatial location such that there
is greater structure in the randomly generated patterns.
See Laffan and Crisp (2003) for an example
(http://www3.interscience.wiley.com/journal/118882020/abstract ), although
there are others out there.
Original issue reported on code.google.com by
shawnlaffanon 30 Jan 2010 at 11:13