Re: [GRASS-user] Feed and manipulate the result of v.distance -pa in python
Nikos Alexandris wrote:
I need to convert the following bash-one-liner:
v.distance --q -pa from=ref_points to=coi_points upload=cat \
column=anycol | cut -d| -f2 | sort -nu | tail -1
into python.
My unsolved problem is that v.distance -pa returns for
example thousands of
lines in the following format:
...
7839|16
7839|17
7839|22
7839|23
7839|24
Reading the main command in python is not the problem
(although I am a bit
confused between grass.pipe, grass.feed, grass.read). Are
there any examples
(scripts in grass trunk maybe?) to follow in order to split
the output, keep
the second column, sort and keep the maximum? Actually
the split is what
worries me most. I 've been looking for quite some time to
find something that
gives me a strait answer but no luck yet.
try v.rast.stats.py: cats.append(line.rstrip('\r\n').split(';')[0])
that splits on ; as the sep, and takes the first entry (column counting
starts at 0 not 1 here)
so for you: line.split('|')[1]
no idea about sorting, but you may be able to program a loop which
starts out empty and only updates if the line's dmax is bigger that the
one stored in the overall variable's, or if the variable is empty (for
the first).
Hamish
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[GRASS-user] Feed and manipulate the result of v.distance -pa in python
Hi! I need to convert the following bash-one-liner: v.distance --q -pa from=ref_points to=coi_points upload=cat column=anycol | cut -d| -f2 | sort -nu | tail -1 into python. My unsolved problem is that v.distance -pa returns for example thousands of lines in the following format: ... 7839|16 7839|17 7839|22 7839|23 7839|24 Reading the main command in python is not the problem (although I am a bit confused between grass.pipe, grass.feed, grass.read). Are there any examples (scripts in grass trunk maybe?) to follow in order to split the output, keep the second column, sort and keep the maximum? Actually the split is what worries me most. I 've been looking for quite some time to find something that gives me a strait answer but no luck yet. The idea is to feed later on v.what.vect with a dmax= as this seems to reduce the eXtremely slow v.distance process as suggested by MoritzL in [1] (v.distance is running for 2 days here over large files[*]!). I timed two different versions of v.what.vect (with and without dmax=) and it seems to make a difference (tested however in small spearfish vector data). All this as part of a horrible script of mine [2]. I feel however that this fits as an enhancement to v.what.vect itself. Regards, Nikos --- [1] http://lists.osgeo.org/pipermail/grass-user/2009-May/050330.html [*] e.g. first result after 10h: Finding nearest lines... Finding nearest areas... 404347 categories read from the map 404347 categories exist in the table 404347 categories read from the map exist in the table 404347 records updated ... [2] Script pareto_3 within the tarred attached file in http://trac.osgeo.org/grass/ticket/804 ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
