[R-sig-Geo] comparing raster and vector data with Grass/R

[Jonathan Greenberg]

Our primary developer for starspan (I designed the program, but did none of
the coding) has since moved on to bigger and better things, but I would
LOVE to get some help getting starspan cleaned up so it can be a GRASS
add-on.  If anyone is interested, please send me an email about it --
ultimately I'd like to write this up for a short paper in Computers and
Geosciences, and I'd be happy to make anyone who wants to take over the
coding aspect a co-author...

--j

(P.S. Email me at greenberg at ucdavis.edu, I need to update my email on this
listserv)


On 3/7/07 12:33 PM, "Roger Bivand" <Roger.Bivand at nhh.no> wrote:

> On Wed, 7 Mar 2007, Schmitt Thierry wrote:
> 
>> I am struggling to overlay spatialLinesDataFrame and
>> SpatialGridDataFrame. The overlay method doesn't allow me to do so.
>> 
> 
> There is no overlay method, you would need to write one, or interpolate
> points along your lines and overlay the resulting point object on the
> raster.
> 
>> As mentioned by matt, I might have a look at starspan. However, I might
>> be interested to have some solution within the Grass/R interface
> 
> Could I suggest that you try v.to.rast in GRASS, and simply use multiple
> rasters? You may need care with the resolution, but in spearfish:
> 
> v.to.rast input=roads output=v_roads use=cat
> 
> then in R:
> 
> library(spgrass6)
> sp <- readRAST6(c("v_roads", "elevation.dem"))
> summary(sp)
> sp1 <- as(sp, "SpatialPixelsDataFrame")
> summary(sp1)
> sp2 <- sp1[!is.na(sp1$v_roads),]
> summary(sp2)
> by(sp2$elevation.dem, sp2$v_roads, summary)
> 
> which just preserves the raster cells crossed by roads as defined by
> v.to.rast.
> 
> Hope this helps,
> 
> Roger
> 
>> 
>> Thierry
>> 
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>> 


-- 
Jonathan A. Greenberg, PhD
Postdoctoral Scholar
Center for Spatial Technologies and Remote Sensing (CSTARS)
University of California, Davis
One Shields Avenue
The Barn, Room 250N
Davis, CA 95616
Cell: 415-794-5043
AIM: jgrn307
MSN: jgrn307 at hotmail.com