[R-sig-Geo] reading WKB geometry

[Edzer Pebesma]

Jaime, I've been successful in reading points from a PostGIS data base 
through OGR; see

http://wiki.intamap.org/index.php/PostGIS
--
Edzer


Jaime Carrera wrote:
> Hi list,
>
> I've been looking around trying to solve this problem; unfortunately I 
> haven't found a way to solve it.
> I have a database with sampling points with an associated sampling 
> date and would like to plot the density of sampling points on a 
> monthly basis for one year using spplot. However, I need to query the 
> database and import the result of the query into R to visualize the 
> data. I can import the query on a column-wise basis but the WKB data 
> are imported as chars into R (as expected). Is there a way by which I 
> could read these data (WKB geometry) once imported into R? Or is there 
> a way by which ReadOGR can read the outcome of the query?
> I tried creating a temporary table through the query, but it seems 
> that ReadOGR can't read it.
>
> Thanks for your help,
>
> Jaime
>
> As an example:
> > db.execute("select geo.id as id,geo.wkb_geometry as geom from wells 
> as geo, gwhead as h where geo.id=h.id and 
> date_part('year',h.date)=2001 and h.gwhead<700",clear=F)
> > ids<-db.read.column("id",as.is=F)
> > geom<-db.read.column("geom",as.is=F)
> Warning message:
> In rpgsql.cast.values.default(data.col) :
>  Coercing PGSQL type 16437 to character
> > geom
>  [1] "0101000020FF7F00000000000088FD2141000000C09BB95741"
>  [2] "0101000020FF7F00000000000088FD2141000000C09BB95741"
>  [3] "0101000020FF7F00000000000088FD2141000000C09BB95741"
>  [4] "0101000020FF7F00000000000088FD2141000000C09BB95741"
>  [5] "0101000020FF7F00000000000088FD2141000000C09BB95741"
>
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-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster, 
Weseler Straße 253, 48151 Münster, Germany.  Phone: +49 251 
8333081, Fax: +49 251 8339763  http://ifgi.uni-muenster.de/