from adehabitat to grass

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Hi all.

For the project AniMov [1] we are trying to export R objects of class "area" 
from adehabitat [2] for use in GRASS 5.7 (immage at: 
www.faunalia.com/animov/area.png).
We tested the following paths:
1. use dxf as an exchange format: this does not work, because the format is 
dxf, which requires a non-free library, and the recompilation of grass
2. use the modules for writing shapefiles (area2shape and export.shape) from 
Clement Calenge (the author of adehabitat). Resulting shapes can be read by 
qgis [3], but not by grass, for unknown reasons (see a sample at: 
www.faunalia.com/animov/test1.zip); there might be something wrong here, 
because also using the library "shapefiles" importing and exporting a valid 
shapefile we get the same result (sample at: 
www.faunalia.com/animov/test2.zip).

I believe it would be better to import "area" objects directly, but the
module R-GRASS apparently cannot do that. Is there any suggestion?

All the best.
pc
- --
Paolo Cavallini
cavallini at faunalia.it   www.faunalia.it   www.faunalia.com
Piazza Garibaldi 5 - 56025 Pontedera (PI), Italy   Tel: (+39)348-3801953
http://pkg-grass.alioth.debian.org/cgi-bin/wiki.pl
============================
[1] http://www.faunalia.com/animov/
[2] http://cran.r-project.org/src/contrib/Descriptions/adehabitat.html
[3] http://qgis.org/
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Neither of the R functions you mention: area2shape() and export.shape(),
are in packages ade4 or adehabitat. Using the R maptools package, your
test1.* and test2.* are readable (so readable with shapelib), but test1.*
has overlapping polygons. If we could convert "area" objects to the
current "polylist" or future package sp representations, the
write.polylistShape() function (using shapelib) in maptools could be used.

A current effort in R is to establish foundation classes - which will let
us have many-to-one, one-to-many converters. So a first step will be to
convert area to some such class, then write that as a polygon shapefile.
Which GRASS shapefile reading program are you using (which version)?

I believe it would be better to import "area" objects directly, but the
module R-GRASS apparently cannot do that. Is there any suggestion?

No, not "area" class objects. Then we get many-to-many. It is much better
to reduce to a single foundation class set first, then the interface would
work for all points, lines, polygons, etc., without having to write a
separate interface for each R class.

For vector, it will be some time before the GRASS libaries are as stable
as raster is and sites were, so using loose coupling through files is more
robust for now. The interface can be extended to do this using system() in
R. Is it worth putting a "new generation" R/GRASS interface based on the
current one on sourceforge?

Best wishes,

Roger