[GRASSLIST:231] Re: Terrain classification R-->GRASS [solved]

[Dylan Beaudette]

On Thursday 16 March 2006 01:24 pm, Dylan Beaudette wrote:
> Hi Roger,
>
> I have been following the directions in the lastest GRASS newsletter in
> regards to moving GRASS6 data to and  from R.
>
> e.g. :
> library(spgrass6)
> gmeta6 <- gmeta6()
>
> x <-
> readFLOAT6sp(c("er9","crosc","longc","slope_n","profc","minic","maxic"))
>
> I have been attempting to reproduce your terrain classification example in
> a paper that you wrote some time ago [1]. I am having a difficult time
> understanding how the results from the clara() clustering results can be
> applied converted back into a raster and sent to GRASS.
>
> here is what I have done so far:
>
> #make a matrix of "observations"
> morph <- data.frame(cbind(x$er9, x$crosc, x$longc, x$slope_n, x$profc,
> x$minic, x$maxic))
>
> #assign names
> names(morph) <- c("er9","crosc","longc","slope_n","profc","minic","maxic")
>
> #perform the clustering
> require(cluster)
> morph.clara <- clara(morph, k=5, stand=T)
>
> #print a summary
> print(data.frame(morph.clara$clusinfo))
>     size  max_diss  av_diss isolation
> 1 121180  9.087186 2.110414  2.964906
> 2  69129  6.820200 2.041174  2.835463
> 3  84236 13.193372 2.561544  3.556510
> 4  53631 16.692732 2.725165  6.939917
> 5  70032 10.193958 1.827320  4.085314
>
> #combine clustered results into a matrix and send to GRASS:
> #original raster was 544 rows by 732 cols:
> morph.image <- matrix(morph.clara$clustering, nrow=544, ncol=732, byrow=T)
>
> #look at the results:
> image(morph.image)
>
> #... it is rotated 90deg CCW !
> (see attached)
>
> In your paper [1] you mention that GRASS and R make different assumptions
> about the indexing of a matrix... however, I cannot quite figure out from
> your example how to rotate this matrix... or if I am even doing this
> correctly.
>
> Any thoughts would be greatly appreciated.
>
> Thanks,
>
>
>
>
> [1] Roger Bivand. Integrating GRASS 5.0 and R: GIS and modern statistics
> for data analysis. Internal Paper (?)


Well here I go again, replying to myself!

Looks like the answers were right in front of me. It is possible to add some 
data back into the original sp-object that was read in from GRASS!!

I have posted details here:
http://casoilresource.lawr.ucdavis.edu/drupal/node/221

Thanks go to those who contributed to the GRASS newletter no.3 regarding GRASS 
and R.

Cheers,




-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341