[R-sig-Geo] maptools and rgeos

[Roger Bivand]

On Thu, 6 May 2010, Ben Madin wrote:

> G'day all,
>
> Please excuse my not finding this, but having just upgraded maptools, 
> there appears to be some issue over gpclib - not looking for trouble, I 
> installed rgeos from r-forge, and it seems to be loadable, but loading 
> maptools I still get the following message.
>
>> library(rgeos)
> Loading required package: sp
> GEOS runtime version: 3.2.0-CAPI-1.6.0
>> library(maptools)
> Loading required package: foreign
> Loading required package: lattice
>
> 	Note: polygon geometry computations in maptools
> 	depend on the package gpclib, which has a
> 	restricted licence. It is disabled by default;
> 	to enable gpclib, type gpclibPermit()
>
> Checking rgeos availability as gpclib substitute:
> FALSE
>>
>
> Have I missed something on installation?(I'm using William Kyngesbury's 
> GEOS Frameworks)

No, thanks for taking this up, and for attention to detail. Both maptools 
and spatstat now warn explicitly about the license problems with gpclib. 
We had hoped to have rgeos ready by now, but interfacing GEOS has turned 
out to be harder than anticipated.

The maptools development code had been modified to use rgeos if available 
- by a call to require(), and the inclusion of rgeos in the Suggests: 
field in the package metadata. Before rgeos had been advanced to release 
status, a serious problem was spotted (by Brian Ripley) in the maptools C 
code for reading GSHHS files, triggering a premature release. In this 
premature release, as can be seen in the ChangeLog:

http://cran.r-project.org/web/packages/maptools/ChangeLog

rgeos was hidden, and all links were commented out. Until rgeos is ready 
for returning to Suggests: status, use of the "drop in" rgeos functions 
has to be manual, so instead of say unionSpatialPolygons() in maptools, 
use unionSpatialPolygonsGEOS() in rgeos (and look at the examples on the 
help page, trying them out to see that the rounding problem has now been 
resolved).

R has (once again) had deserved success in the Google Summer of Coding, 
and rgeos is one of the projects that has been adopted. Some of the 
original difficulties have now been resolved, and I hope that the package 
will be greatly improved compared with my "muddling through" first cut at 
the GEOS interface.

Hope this clarifies things a little,

Roger

>
> cheers
>
> Ben
>
>
>
> sessionInfo()
> R version 2.10.1 Patched (2010-02-01 r51089)
> x86_64-apple-darwin9.8.0
>
> locale:
> [1] en_AU.UTF-8/en_AU.UTF-8/C/C/en_AU.UTF-8/en_AU.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] maptools_0.7-34 lattice_0.18-3  foreign_0.8-40  rgeos_0.0-9     sp_0.9-62
>
> loaded via a namespace (and not attached):
> [1] grid_2.10.1  tools_2.10.1
>
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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