[GRASS-dev] v.cellstats script [+new module: r.out.xyz]

[Hamish]

Martin Wegmann wrote:
> Carlos Grohmann and I created a script as substitute for v.cellstats.
> It would be great if somebody can look through it to give feed-back
> how to improve it before we post it to the WIKI.

Hi Martin,


how does this script's function differ from the new r.resamp.stats
module?


script notes:   (many are general comments for all grass scripts)


* _v._cellstats, but it imports and exports raster maps!

* use standard input= and output= option names for consistency.
  make input= the first option

* output maps should use the "new,cell,raster". This way --overwrite
works, etc
#% key: raster
#% gisprompt: old,cell,raster

* for method key, use "options:" line to specify available methods.
#% options: n,min,max,range,sum,mean,stddev,variance,coeff_var

* redirect status messages to stderr:  (helps parsing output to a file)
echo "You must be in GRASS GIS to run this program" 1>&2

* export cell x,y,z to file directly:
was:
  #convert to vect and export as ascii
  r.to.vect -z input=$GIS_OPT_raster output=tmp_vect feature=point
  v.out.ascii input=tmp_vect output=xyz_file format=point
easier:
  r.stats -1ng "$GIS_OPT_raster" > xyz_file

(as this is impossible to guess without prior experience, I've just
written a simple wrapper script called r.out.xyz, now in 6.3cvs.
maybe better as an option to r.out.ascii?)

* use "r.to.vect -b" so the script can work with larger grids 
(1500x1500) input -> 2.25million vector point & memory problems
if topology is built. Also, r.in.xyz has to keep the entire map in
memory, so hard-coding percent=100 for Very large grids could cause
problems.

* use g.tempfile  (script won't work if in a non writeable dir, eg "/")
see grass scripts/ for an example of doing that safely
(e.g. r.univar.sh)

* double quote all "$VARIABLES". legal map names may include restricted
shell chars, filenames may include spaces.


cheers,
Hamish