On 28/02/08 20:12, Tom Russo wrote:
On Thu, Feb 28, 2008 at 06:54:09PM +0100, we recorded a bogon-computron collision of
the <[EMAIL PROTECTED]> flavor, containing:
On 28/02/08 16:39, Tom Russo wrote:
I have been trying to wrap my brain around "multi-layered" GRASS vectors and
have only succeeded in wrapping my brain into knots. Perhaps someone here
with a solid understanding of this stuff can help me.
[...]
Since I'm rambling now, I'll just cut to the chase and ask my question:
Given a GRASS vector with two attached database tables, one of which (layer
2, attaching attributes to centrois) has a key field POLYID, how can I
create a new layer using a third, much smaller table, that also has a
POLYID field, such that the new layer only contains that subset of
centroids where the third layer table's POLYID matches layer 2's POLYID
for that centroid?
I think at this stage your best bet is probably to do something like this:
v.category OldMap option=add layer=3 out=NewMap
#find a link between the category numbers created and the original
# categories, this should work:
v.build OldMap option=cdump > TempFile
# You will have to edit TempFile to only take into account layer 2 and
# then find a way to import the results into your database
With the potential for tens of thousands of records, anything
involving manually editing a dump of categories seems an unworkable solution.
With awk / sed magic this should not be too complicated to automate...
Moritz
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