Hi Eric,
Maybe you could test on, or parse the output of, g.list vect=dummymap?
At 21:35 11-10-2006, you wrote:
Jeroen,
Thanks, I hadn't thought of using v.select before. One problem with using
v.select is that even if no output file is produced (i.e., ainput and binput
don't overlap), the exit status from the program is still 0, which it should
be, as no error was produced. So a different test for whether a vector was
produced would be needed.~ Eric.
-----Original Message-----
From: Jeroen Wortel
To: Patton, Eric; 'grassuser@grass.itc.it'
Cc: 'grass-dev@grass.itc.it '
Sent: 10/11/2006 3:07 PM
Subject: Re: [GRASS-user] How to find whether one vector is contained by
anotherHi Eric,
you could use a script that goes through the available vector tracks
and do for each a v.select option=overlap output=dummyfile. The
contents of the output map are not important, but the fact that it is
created or not. You could then check in your script if it was created
or not. If it is created, the vector track touches the polygon
comprising your region of interest.A nice addition to Grass would be vector selections that are kept in
memory instead of written to an output file. Only the pointers to the
geometry need to be kept in memory, no actual geometry. These
selection could be used in other grass commands just like normal
vector maps. This mechanism works for example in GenaMap (called
active ID's) and is very powerful for scripting purposes and saves a
lot of temporary files on disk. (This would mean however that vector
indices should be kept in the vector files instead of created every
time)that
When doing a selection inside or a proximity in GenaMap, the number
of selected features is returned.At 20:09 11-10-2006, Patton, Eric wrote:
>A lot of time I get requests to find out what vector navigation
tracklines
>fall within a certain region. This is easy to do by visual inspection
>(turning on and off vectors in gis.m) when the number of vectors is
low, but
>becomes too much work for large numbers (i.e., 200). What is the best
way to
>find out if one vector is contained by another, without writing any
output?
>All I need is a listing of vector names.
>
>I was thinking maybe set up a bash switch statement to look at a set of
>cases between the vector's region extents and the extents of the region
in
>question. It seems to me there would be a lot of scenarios to consider
and
>would be really complex (i.e, north_map < north_region && north_map >
>south_region && ...)
>
>Is there any existing vector program that performs this functionality
>already? If not, what do you think would be the best approach to solve
this
>problem?
>
>~ Eric.
>
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