[R] writing polygons/segments to shapefiles (.shp) or other ArCGIS compatible file

[Stephane DRAY]

There is a little problem with the approach I described in my previous email.
In ADE-4, coordinates are given in pixel and so Y are inverted. You must 
invert your Y coordinates to obtain the good representation in ArcView. An 
example:

 > library(ade4)
 > library(shapefiles)
 > library(maptools)
 > try1 <- read.shapefile(paste(ShapeDir, "columbus", sep="/"))
 > shppolys <- shape2poly(try1, as.character(try1$dbf$dbf$NEIGNO))
 > obj=poly2area(shppolys)
 > obj[,3]=-obj[,3]
 > write.table(obj,"try.area",col.names=F,quote=F,row.names=F)
 >

Then, use the 'From AREA' function in AVADE.



At 10:32 25/02/2004, Patrick Giraudoux wrote:
>I am not sure a previous e-mail reached the list (no mail aknowledgement 
>from R-boundle etc.). The question was how to write polygon
>or segment coordinates into a shapefile set or any other ArcGIS supported 
>format. The library shapefiles seems to do something but
>the documentation is a bit beyond of my mind.... and I cannot get the 
>meaning of the functions write**** and its application to the
>case below:
>
>In simple words, is there a somewhere a function taking polygon 
>coordinates (or simple segments) within R to a "ready to read" set
>of files ***.shp, ***.shx, etc...
>
>Thanks in advance for any hint
>
>Patrick
>
>
>
>----- Original Message -----
>From: "Patrick Giraudoux" <patrick.giraudoux at univ-fcomte.fr>
>To: "r-help" <r-help at stat.math.ethz.ch>
>Sent: Wednesday, February 25, 2004 1:08 PM
>Subject: writing polygons/segments to shapefiles (.shp)
>
>
> > Dear all,
> >
> > The library maptools offers a fantastic support for shapefile reading.
> >
> > Is there a R library available permitting the writing of polygon or 
> segment coordinates into shapefile?
> >
> > Thanks for any hint,
> >
> > Patrick Giraudoux
> >
> >
> >
> >
>
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Stéphane DRAY
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Département des Sciences Biologiques
Université de Montréal, C.P. 6128, succursale centre-ville
Montréal, Québec H3C 3J7, Canada

Tel : 514 343 6111 poste 1233
E-mail : stephane.dray at umontreal.ca
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