[GRASSLIST:7734] operations on subsets of data in database

GRASS GRASS user
1

I figured out how to set up attribute data for a point layer in a mysql database. Very handy because I can now select points for display based on attributes (population > n, type like “whatever”, etc.) However, now I want to perform operations on those data based on the same select criteria. For example, I want to create buffer vector layer from just some of the points in that point layer. There does not appear to be any way to do this in GRASS. I would have to create a copy of the layer or a new layer that contains a subset of the points. This seems like such a obviously useful feature that if there is no way to currently do this, I’d like to suggest that it be considered in GRASS’s development. After all, what’s point in having the wonderful capability of selecting geometry with a database query if all you can do with it is display it?

Just my 2 cents.

Jason Horn

Boston University Department of Biology

5 Cumington Street Boston, MA 02215

jhorn@bu.edu

office: 617 353 6987

cell: 401 588 2766

2

On Thu, 28 Jul 2005 23:32:20 -0400
Jason Horn <jhorn@bu.edu> wrote:

I figured out how to set up attribute data for a point layer in a
mysql database. Very handy because I can now select points for
display based on attributes (population > n, type like "whatever",
etc.) However, now I want to perform operations on those data based
on the same select criteria. For example, I want to create buffer
vector layer from just some of the points in that point layer. There
does not appear to be any way to do this in GRASS. I would have to
create a copy of the layer or a new layer that contains a subset of
the points.

[more old emails...]

v.extract where=<SQL query>

Many vector modules have similar functionality.

?
Hamish