[R-sig-Geo] Map2points() substitute for class "map"

[Fernando Mayer]

Hi,

following Tanimura et al. 2006 (Proportional Symbol Mapping in R) [1], 
I'm trying to implement the ProportionalSymbolMap function for maps of 
class "map" (produced by the maps package), instead of maps of class 
"Map" (imported from a GIS polygon vector file). That function uses 
the Map2points() function to (as far as I could understand) extract 
the points (i.e. map boundaries) from a "Map" object to a n x 2 
matrix, as in

 > verts <- Map2points(map)[order(variable, decreasing = T),]

What I tried to do to substitute this function was

 > verts <- matrix(c(map$x,map$y),ncol=2)[order(variable,
	decreasing = T),]

where map is an object of class "map". But, that doesn't work. As I 
have no experience with shapefiles, I'm restricted to know what 
exactly Map2points() does and if there is some other function that can 
do the same thing for a "map" object.

BTW, if trying to implement this function (ProportionalSymbolMap) for 
a "map" object (instead of a "Map") is not a good idea (because all 
the rest of the function), please let me know. I think (on my limited 
knowledge on this) that with same adjustments it may be possible.

[1] http://www.jstatsoft.org/v15/i05/v15i05.pdf

Thanks for any hint,
-- 
Fernando Mayer
Grupo de Estudos Pesqueiros - GEP
Centro de Ciências Tecnológicas, da Terra e do Mar - CTTMar
Universidade do Vale do Itajaí - UNIVALI
Itajaí - SC - Brasil
e-mail: fernandomayer [@] gmail.com