[GRASSLIST:141] Re: How to report length totals for all lines matching specific ID

[David Finlayson]

In GRASS that would be something like this (note the comma I forgot in
last post):

echo "select first(CLASS), sum(SEG_LENGTH) from <table_name> group by
CLASS" | db.select

You pipe the query to your database through db.select. Alternatively,
if you are using a database like sqlite you can do the query right in
the database.


On 3/15/06, David Finlayson <david.p.finlayson at gmail.com> wrote:
> On 3/15/06, David Finlayson <david.p.finlayson at gmail.com> wrote:
> > If you are using a database for your attributes can't you just run an
> > SQL query? Something along the lines of:
> >
> > select first(CLASS) sum(SEG_LENGTH) from <table_name> group by CLASS;
> >
> >
> >
> > On 3/15/06, Patton, Eric <epatton at nrcan.gc.ca> wrote:
> > > I have a vector of a coastline; the coast is segmented into different
> > > coastal types, according to unique IDs:
> > >
> > > CAT Class_ID CLASS         SEG_LENGTH
> > > 1   5        Rock Cliff    56.789000
> > > 2   7        Barrier Beach 13.450000
> > > ....
> > >
> > >
> > > I successfully popluated the SEG_LENGTH column with the length of each
> > > segment using v.to.db:
> > >
> > > v.to.db Coastal_Classes option=length type=line units=m
> > >
> > > Now I want to report total lengths of each CLASS (i.e., total length of all
> > > "Rock Cliff" segments, etc.)
> > >
> > > Any ideas?
> > >
> > > ~ Eric.
> > >
> > >
> >
> >
> > --
> > David Finlayson
> >
>
>
> --
> David Finlayson
>


--
David Finlayson