Hi all,
I am trying to setup a geospatial CAR model to implement areal spatial
smoothing (similar to Fig11.11 in "Applied Spatial Data Analysis with R" except
without the beta term).
I am using ESRI shapfiles downloaded from Census Ireland
(http://www.cso.ie/en/census/census2011boundaryfiles/)
As some of the boundaries have changed over various census years, I need to
join certain polygons - note these are adjacent polygons and I have used
unionSpatial Polygons to try to do this. I am using a join_list of polygons
that have changed and are to be joined - this is just a CSV file I made myself.
The problem I am having is that my code is not joining the correct polygons and
is in fact joining non-adjacent unrelated polygons. I can't figure out how to
fix this.
My code looks like this: (FYI - EDdata contains a unique code for each polygon
in a factor variable called GEOGID).
EDdata<-readOGR(".","Census2011_Electoral_Divisions_generalised20m",TRUE)
names(EDdata)
join_list<- read.csv("joins.csv", header=TRUE)
ED2<-merge(EDdata,join_list,by="GEOGID",all=TRUE)
# modify copied geogids as per join list
ED2$GEO<-as.character(ED2$GEOGID)
ED2$GEO[!is.na(ED2$Joined)]<-as.character(ED2$Joined[!is.na(ED2$Joined)])
ED2$GEOGID2<-as.factor(ED2$GEO)
# apply join function to polygons
EDdata$GEOGID2<-ED2$GEOGID2
EDpoly_joined <- unionSpatialPolygons(EDdata, EDdata$GEOGID2)
When I plot specific joined polygons they are not the adjacent ones I intended
to join. As far as I can see - GEOGID and GEOGID2 match each other so I am a
loss as to why the unionSpatialPolygons function appears to join to incorrect
polygons.
FYI the join list looks like this (its longer than this but this should give
you an idea).
Joined variable GEOGID
E01001 E01001/01019 Sub1 E01001
E10001 E10001 Sub1 E10001
E10004 E10004 Sub1 E10004
E11001 E11001/11026 Sub1 E11001
E11002 E11002/11055 Sub1 E11002
E11003 E11003/11092 Sub1 E11003
I cannot see where I am going wrong -I'd be very grateful for any
assistance/advice.
Many thanks,
James
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