How to add labels etc. with EIA shapefiles in R?
I'm trying to create a map of US shale basins and I'm very new to creating maps. I have downloaded the shapefiles from the US Energy Information Administration (EIA). I have also, been able to created a basic map with the bases plotted (please see code below). I would like to add labels etc. to this map. I believe these would be in the other files downloaded outside the shapefile.
library(maps) map("state") shapLocation<- "C:/shapfile/shalegasbasin/" pcontorta <- readShapePoly(paste(shapLocation,"US_ShaleBasins_EIA_May2011.shp",sep="")) plot(pcontorta, add=TRUE, col=adjustcolor("black", alpha.f = 0.6), border=FALSE)
Shapefile from: http://www.eia.gov/maps/layer_info-m.cfm
Description of a shapefile: http://en.wikipedia.org/wiki/Shapefile
Take a look at ?text. You can place the labels using the polygon coordinates which will return approximate polygon centroids.
library(sp) Sr1 = Polygon(cbind(c(2,4,4,1,2),c(2,3,5,4,2))) Sr2 = Polygon(cbind(c(5,4,2,5),c(2,3,2,2))) Sr3 = Polygon(cbind(c(4,4,5,10,4),c(5,3,2,5,5))) Srs1 = Polygons(list(Sr1), "1") Srs2 = Polygons(list(Sr2), "2") Srs3 = Polygons(list(Sr3), "3") SpP = SpatialPolygons(list(Srs1,Srs2,Srs3), 1:3) SpP = SpatialPolygonsDataFrame(SpP, data.frame(ID=1:3)) # Plot polygons and place text based on polygon centroids plot(SpP) text(coordinates(SpP)[,1], coordinates(SpP)[,2], paste("p",SpP$ID,sep="-"))