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On 01/02/2014 12:11 AM, Dave Roberts
wrote:
Hi Anna,
On 01/01/2014 01:50 PM, Anna Petrášová wrote:
Hi Dave,
On Wed, Jan 1, 2014 at 3:10 PM, Dave
Roberts
<[email protected]
<mailto:[email protected]>>
wrote:
Friends,
After some alternative approaches to a simple problem
of
compositing rasters (see previous posts, esp. compositing
rasters @9:32)
I developed a very crude function to update rasters
r.update target mask x y
updates raster target by substituting y everywhere that
raster mask
has x. A more GRASS-like syntax would be
r.update target=string mask=string current=integer
replace=integer
I'm not sure if I don't miss anything but why don't you use
r.mapcalc
_expression_ like this:
new = if(mask == x, y, target)
and then
g.rename new,target --overwrite
well probably because I'm not too bright. Obviously your elegant
solution would allow multiple sequential updates just the way I
needed as long as I do the rename --overwrite very time. I knew
there had to e GRASS way to do this, I just hadn't figured it out
yet.
Thanks!
The other quick and dirty workaround could be a combination of
r.reclass and r.series
echo "1=2 \
*=NULL" | r.reclass in=b out=b2
echo "1=3 \
*=NULL" | r.reclass in=c out=c3
then:
r.series in=a,b2,c3 out=target method=max
Using method=max will avoid the problem of cells with values in more
than one original.
Cheers,
Micha
Anna
but my bash skills are pretty limited and I elected (for the
time
being) not to parse the arguments that way. The current
function
relies on a short bash script and a FORTRAN executable. The
crude
part is exporting both the target an mask rasters as ascii
exports,
creating a new ascii file, and doing an r.in.ascii to bring
the
updated raster back in. It only works (at present) for
integer
rasters, but it's intended for thematic maps, so that seems
OK.
r.update.sh <http://r.update.sh> just below.
r.out.ascii inp=$1 out=$1.asc null=-1
r.out.ascii inp=$2 out=$2.asc null=-1
g.remove rast=$1
r_update $1.asc $2.asc $3 $4
r.in.ascii inp=tmp.file out=$1 nv=-1
rm $1.asc
rm $2.asc
rm tmp.file
You have to "alias r_update 'sh r_update.sh'" or name the
script
r.update and chmod +x r.update to make it run as shown.
The FORTRAN code for r_update is at
ecology.msu.montana.edu/GRASS/__r_update.f90
<http://ecology.msu.montana.edu/GRASS/r_update.f90>
The code compiles with gfortran. The executable must be in
your
path, or you can modify the bash script with a full path to
it.
It is my sincere hope that someone with GRASS chops
will write
a function for g.extension that uses the API and avoids all
this
ascii input and output, but this serves as a demo and useful
(if
clumsy) approach in the meantime.
Dave
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~__~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~__~~~~~~~~~~~~
David W. Roberts office
406-994-4548 <tel:406-994-4548>
Professor and Head FAX
406-994-3190 <tel:406-994-3190>
Department of Ecology email
[email protected] <mailto:[email protected]>
Montana State University
Bozeman, MT 59717-3460
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