[GRASSLIST:857] Re: v.segment

[Michael Barton]

Trevor,

If you've got the cat values from v.build the main issue is to get them into
something that GRASS can recognize as an attribute table. You could simply
import them into a spreadsheet and export them as dbf. Then use
v.db.connect. Even better if there was a txt2dbf utility. Maybe someone
knows of one. Or you could try a MySQL or SQLite routine to get the data
into one of those formats.

However, if you want to script this you might try the following:

Redirect the stdout to a file datafile.csv
I think you'd need to add a field name line to the beginning
Replace all the "|" with "," using sed
Use v.in.ogr to read in the csv file
Use v.db.connect to the new attribute file.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton



> From: Trevor Wiens <twiens at interbaun.com>
> Date: Tue, 25 Apr 2006 00:26:41 -0600
> To: Michael Barton <michael.barton at asu.edu>
> Cc: Multiple recipients of list <grasslist at baylor.edu>
> Subject: Re: [GRASSLIST:855] Re: v.segment
> 
> On Mon, 24 Apr 2006 23:00:15 -0700
> Michael Barton <michael.barton at asu.edu> wrote:
> 
>> Use v.category to attach categories.
>> 
>> V.to.db to add information to attribute table? I don't know if this works
>> with v.segment output or not. In fact, I can't figure out how v.segment
>> works either.
>> 
>> Create a dbf file using a spreadsheet (OO or Excel -- OO works better). Call
>> the first column "cat", make it an integer, and fill it with a sequence of
>> numbers equal to the number of points you have. Then use v.db.connect to
>> link them up.
>> 
> 
> Michael,
> 
> Thanks, but not really what I wanted to hear.
> 
> I wrote a script to make stops on Breeding Bird Survey route lines at
> equal intervals, and manipulated the category values to be meaningful.
> 
> Unfortunately, v.segment doesn't create an attribute table so I used
> v.build with the cdump option to get a list of the categories and then
> used db.execute to add them one by one into a table. Very slow.
> 
> I can see now I could get a list easier using v.category, but
> unfortunately it won't automagically create an attribute table with the
> categories in it.
> 
> I was hoping for an easy way to do this as it would make the script a
> lot more elegant and faster, but it appears that my ugly hack is the
> only solution.
> 
> Thanks
> 
> T
> -- 
> Trevor Wiens 
> twiens at interbaun.com
> 
> The significant problems that we face cannot be solved at the same
> level of thinking we were at when we created them.
> (Albert Einstein)