[R-sig-Geo] seamless maps

[Roger Bivand]

On Thu, 8 Jan 2009, Hans-Jörg Bibiko wrote:

>
> On 08.01.2009, at 14:27, Roger Bivand wrote:
>
>> On Thu, 8 Jan 2009, Hans-Jörg Bibiko wrote:
>> 
>>> Hi,
>>> 
>>> I wonder if there's a workaround to generate seamless maps based on 
>>> SpatialPolygons objects. E.g. to produce a map showing Australia at the 
>>> left edge and America at the right one ( xlim := min: 110°E , max: 30°W ).
>>> Or the way around, is there a function to re-center a given map by 
>>> defining the median longitude? (I know the function 'recenter' which 
>>> produce a map from 0° to 360°)
>
>
> Dear Roger and Matt,
>
> many thanks for the hints. I'll have a look at these.
>

A further idea if you don't need the polygons is:

wrld_simpl_SL <- as(as(wrld_simpl, "SpatialPolygons"), "SpatialLines")
wrld_simpl_SL_0_360 <- recenter(nowrapSpatialLines(wrld_simpl_SL))
plot(wrld_simpl_SL_0_360, axes=TRUE, xlim=c(110, 330), ylim=c(-80, 80))

which keeps the correct coordinates but at the cost of losing the polygons 
and a couple of artefact lines at 180°.

Roger

>
> Best,
>
> --Hans
>
> **********************************************************
> Hans-Joerg Bibiko
> Max Planck Institute for Evolutionary Anthropology
> Department of Linguistics
> Deutscher Platz 6     phone:   +49 (0) 341 3550 341
> D-04103 Leipzig       fax:     +49 (0) 341 3550 333
> Germany               e-mail:  bibiko at eva.mpg.de
>
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-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, 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