[R] Projecting data on a world map using long/lat

[mathijsdevaan]

Thanks for the suggestions, but I am not there yet (I'm a real novice). In
the code provided by Patrick (see below), I changed the shape input (from
sids to world) which I downloaded here:
http://thematicmapping.org/downloads/world_borders.php. As a result I also
need to change the "CNTY_ID" and "id" in the code, but I have no idea what
to put there. Could you please help me? Thanks!

Mathijs

library(maptools)
library(ggplot2)
gpclibPermit()

myshp<- readShapeSpatial(system.file("shapes/sids.shp",
package="maptools"))

## see licence, not GPL
myshp.points<- fortify.SpatialPolygonsDataFrame(myshp,
region="CNTY_ID")

shpm<- merge(myshp.points, myshp, by.x="id", by.y="CNTY_ID")

head(shpm)

p <- ggplot(shpm, aes(long, lat, group=group, fill=NWBIR74))
p <- p + geom_polygon() + geom_path(color="white") + coord_equal()

## Add some locations
cities <- read.table(textConnection("
long        lat      city      val
-78.644722 35.818889  Raleigh   323
-80.843333 35.226944  Charlotte  510
-82.555833 35.58      Asheville    400"), header = TRUE)

p <- p + geom_point(aes( fill=NULL, group = NULL, size=val),
         data = cities, color= 'black')
p
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