[R] Plotting shapefiles on existing maps

[Ray Brownrigg]

> From: nhy303 at abdn.ac.uk
> 
> I have plotted a map of the Barents Sea and surrounding coastline using:
> 
> map('worldHires',ylim=c(50,85),xlim=c(5,65),fill=T,resolution=0)
> map.axes()
> map.scale(x=30,metric=T)
> 
> Next, I imported a shapefile with depth contours for the sea:
> 
> contours<-read.shape("D://My Documents/BarentsSea.shp",dbf.data=T)
> 
> (This is in mercator projection).
> 
> Despite extensive searches of the help files and R site, I cannot find a
> way to plot the contours onto the map.  Does anyone have any suggestions?
> 
It is not clear to me exactly what you are having difficulty with, but
if you are able to produce a contour plot from that data, then note that
both contour() and map() have an "add" argument, so as long as the axis
limits are conformant (i.e. both longitude/latitude) you can add one
plot to the other.

Perhaps the trick is in converting your contours data into
longitude/latitude form for the x and y components.

Hope this helps,
Ray Brownrigg