[R-sig-Geo] Projection of a shapefile

[Roger Bivand]

On Tue, 6 Mar 2012, Ester Polaina Lacambra wrote:

> Hello everyone,
>
> This is going to sound quite silly, but I'm an amateur R user and after a
> while I haven't been able to find the solution for my problem...
> I've got a shapefile coming from ArcMap 10, with a Projected Coordinate
> System: World_Cylindrical_Equal_Area (I chose that one when I was measuring
> areas); and a Geographic Coordinate System: GCS_WGS_1984.
>
> I read it with R by using:
>
> WCountries <- readShapePoly("myfile",ID="COUNTRY")
>

readShapeSpatial() in maptools cannot read any projection information - it 
uses shapelib, which ignores projections. Use the readOGR() function in 
rgdal instead. Do not be surprised if the Arc description is not matched, 
it is not a gold standard; an EPSG code has at least as good authority.

The coordinates you see are what you asked Arc to export, they are in the 
coordinate reference system you specified.

Roger

>
> When I use the expresion "coordinates(WCountries)" some apparently UTM
> coordinates appear. How do I know how R has calculated this? because
> it keeps saying:
>
>
> Is projected: NA
> proj4string : [NA]
>
>
>
> Thank you very much!!
>
>
>

-- 
Roger Bivand
Department of Economics, NHH Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no