[R] SpatialPolygonsDataFrame holes problem
dbebber at earthwatch.org.uk
Sat Jul 9 10:40:55 CEST 2011
I have obtained shapefiles for Indian states from here:
Problem: I want to extract centroid coordinates for each State, but there is some coding problem with the shapefiles that prevents this.
#After extracting the shapefiles from the india_state.zip file, then:
india <- readShapeSpatial("india_state.shp")
#Some states are made up of more than one polygon.
#State names are in the NAME column of the dataframe
india at data
plot(india[india$NAME == "Tamil Nadu",], col = 1:8)
#Extract centroid for a State (this works):
gCentroid(india[india$NAME == "Tamil Nadu",])
#Error arises for this State:
gCentroid(india[india$NAME == "Gujarat",])
#Error in createPolygonsComment(p) :
#rgeos_PolyCreateComment: orphaned hole, cannot find containing polygon for hole at index 2
I don't know my way around SpatialPolygonsDataFrame objects very well, and have no idea how to fix the errant hole.
Any help greatly appreciated.
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