[R-sig-Geo] Replace a polygon by a new one of a SpatialPolygonsDataFrame

[Hans-Jörg Bibiko]

Thanks a lot!!!

@Edzer: wrld_simpl at polygons[237] <- theNew
doesn't work. Also due to [<- declaration

@Barry: Yes, removing the old entry and adding the new one via rbind works :) - of course. The clue is to recreate the entire SpatialPolygonsDataFrame. (And sorry for a non-closed polygon ;) )

For the records, I ended up with the following (also in terms of not changing the plot order and the indices):

library(maptools)
data(wrld_simpl)

r <- bbox(wrld_simpl[237,])

theID <- wrld_simpl[237,]@polygons[[1]]@ID

theNew <- list(Polygons(list(
	Polygon(cbind(c(r[1,1],r[1,1],r[1,2],r[1,2],r[1,1]),c(r[2,1],r[2,2],r[2,2],r[2,1],r[2,1])))), 
	theID))

# item which has to be replaced
replace_index <- 237

ws <- wrld_simpl[replace_index,]
wsb <- SpatialPolygonsDataFrame(SpatialPolygons(theNew), data=ws at data)
proj4string(wsb) <- proj4string(wrld_simpl)

wrld_simpl_new <- rbind(wrld_simpl[1:(replace_index-1),], wsb, 
	wrld_simpl[(replace_index+1):dim(wrld_simpl)[1],])

wrld_simpl_new at plotOrder <- wrld_simpl at plotOrder

plot(wrld_simpl[237, ])
plot(wrld_simpl_new[237,], border="red", add=T)


Again, thanks a lot, you saved my day :)

Best, Hans