XP, R and Tinn-R up to date.

Greetings:
I've been away from the list for quite some time, and (as expected) some things change. My understanding is that maptools contains "unionSpatialPolygons". However, the following code (which previously worked):
#______________________________________________________________
library(maptools)
msa_cmsa <- readShapePoly("1999_MSA_CMSA") # puts shapefile in SpatialPolygonsDataFrame
summary(msa_cmsa)
msa_cmsaaggregated=unionSpatialPolygons(msa_cmsa, msa_cmsa$MSACMSA)
#_______________________________________________________________
leads to:

> msa_cmsaaggregated=unionSpatialPolygons(msa_cmsa, msa_cmsa$MSACMSA)
Loading required package: gpclib
Error in as(pli[[1]], "gpc.poly") : 
  no method or default for coercing "matrix" to "gpc.poly"
In addition: Warning message:
In library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called 'gpclib'

May I ask for a hint?

thanks,

mihai





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