[R-sig-Geo] Compile sf in windows with liblwgeom

[Edzer Pebesma]

On 16/09/17 18:22, Barry Rowlingson wrote:
> 
> 
> On Sat, Sep 16, 2017 at 3:45 PM, Edzer Pebesma
> <edzer.pebesma at uni-muenster.de <mailto:edzer.pebesma at uni-muenster.de>>
> wrote:
> 
> 
> 
>     On 16/09/17 15:20, Eduardo Diez wrote:
>     > Dear list,
>     > I have a MULTIPOLYGON geometry set where the rings are in the wrong
>     > direction and would like to correct that with *st_make_valid*. As I'm in
>     > Windows and use the binary version of the *sf* package it gives me the
>     > error:
>     >
>     >> sp2 = st_make_valid(sp1)
>     > Error in CPL_make_valid(x) :
>     >   st_make_valid requires compilation against liblwgeom
>     >
>     > Is there a series of steps I can follow for compiling *sf* in Windows
>     > linked to liblwgeom?
> 
>     No, and I also don't think that st_make_valid does this.
> 
> 
> st_make_valid certainly did something:
> 
> https://gis.stackexchange.com/questions/254836/sf-lines-to-polygons-with-holes

I only tried a single outer ring in both directions, and it didn't
revert them. Maybe it only reverts if if outer and inner ring have the
same direction.

> 
> I've just added an edit to my answer there with the sp-and-back round
> trip, which seems to work, but its not exactly the most satisfying solution.

It would be fairly trivial to move some of the code to sf - at a
performance penalty if we'd do the check always, like sp does.

> 
> What's the problem with liblwgeom on Windows?

It's not part of the rwinlib collection at https://github.com/rwinlib ;
I'll bring it up with Jeroen next time I see him. lwgeom has more good
things than what sf uses.

> 
> Barry
> 

-- 
Edzer Pebesma
Institute for Geoinformatics  (ifgi),  University of Münster
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/

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