[GRASSLIST:3381] Re: Category labels in dig_cats

[Eric G. Miller]

On Mon, Mar 25, 2002 at 06:56:53PM -0600, S P Arif Sahari Wibowo wrote:
> Hi!
> 
> I just started using GRASS 5.0. Great program! Thanks to all who
> contribute the development!
> 
> I have question about the category labels in dig_cats. I imported a
> vector-based map from .e00 format using m.in.e00, and it produced several
> category label files in dig_cats for each layer (e.g. roads.roadclass,
> roads.num-lanes, roads.interst#, roads.us#, etc. for roads layer). As I
> search in this mailing list archive, it seems that GRASS cannot [yet] deal
> with multiple label files, only one at the time.
>
> Below I have several questions about GRASS:
> 
> 1. Are the labels only for labeling / naming objects, or GRASS can
> actually consider it as 'property' of the objects, and therefore can draw
> objects with appearance depend on this 'property' (label)? Or are there
> different attributing mechanism for this purpose?

Pretty much just label purposes.  There are some programs that will use
the dig_att file (which maps the feature to the category) via the
category number.  For the .e00 output, just use softlinks to change the
active "label".  There is some support for attributes via the postgresql
modules (and db. ones).  Though, it's not quite fleshed out.

There's some support for drawing via category numbers.

> 2. How to make a map drawing that also display the category labels for
> each objects?

d.vect.labels is one possibility.

> 3. If for each category I combine all the labels of that category, and put
> it in new category labels' file, will this work? Will I lost some
> functionality because of this combining of labels?

Maybe.  You might run into some line length restrictions.

> 4. How to create a new layer that contain a subset of an old layer, only
> the objects that have certain condition in its category labels (e.g. '>0',
> '<>"CI"', etc.)?

Unfortunately, not quite there.  Some possibilities via v.reclass and a
couple other modules.  It's related to not have good attribute handling.

> 5. How to make a 'display set' that contain several vector layer, each
> have their own appearance, that will be drawn together, exported together,
> printed together, etc.?

ps.map? Or just draw them all to a "monitor" (which may be a pixmap).

> 6. Any idea on a path of exporting vector format from GRASS to other
> formats accessible to end-user layout / business applications (StarOffice,
> Freehand, MS Office, etc.)?

Not much support for that.  Maybe via dxf files? or xfig format?

-- 
Eric G. Miller <egm2 at jps.net>