Thanks Hamish. It seems only likely that such a routine would exist.
Here's the part where I need a little help though. It appears that
v.distance from=pnt to=area dmax=0 upload=cat column=areacat
will find and report the cat number of the polygon that points lie
within, and I can use that in a database operation which is extremely
handy. So, I have done that, and now the area cat for each point is
available in the database. That works for points in a point vector
feature.
Using d.what.vect or v.what, however, I cannot control whether the
function reports a boundary or centroid. This makes it hard to
replicate the behavior of v.distance for a few points on the fly.
Is there some way to access the existing point-in-polygon routine from
an existing GRASS function to simulate what I'm after?
Looking at the progammer's manual, writing something like v.pip (= to
d.what.vect reporting always area cat) appears to be a bit more than I
want to bite off at present.
Perhaps one approach would be
d.where > file
(edit file as necessary for separator)
v.in.ascii in=file out=points fs=whatever
v.distance from=points to=area dmax=0 upload=cat column=areacat
That works but seems like a lot of work for what I'm after.
Thanks much, Dave
Hamish wrote:
Dave wrote:
I think it would indeed be handy if a switch
was added to v.what and
d.what.vect in GRASS 7. In the meantime it might be
handy to write a v.pip command for GRASS 6. I have
written a point-in-polygon routine for other software
(including R), but I would have to really study the file
structures of GRASS vectors to attempt that in
GRASS. If any GRASS programmers are
interested let me know and perhaps we could work it out as
an add-on.
point in polygon is a standard function in the vector library for
years.
Hamish
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