[GRASS5] d.vect.area

[M Lennert]

From:           	Glynn Clements <glynn.clements at virgin.net>
Date sent:      	Thu, 31 Jan 2002 16:03:39 +0000
To:             	"M Lennert" <fa1079 at qmul.ac.uk>
Copies to:      	grass5 at grass.itc.it
Subject:        	Re: [GRASS5] d.vect.area

> 
> M Lennert wrote:
> 
> > I was just wondering, Eric, why you decided to implement 
> > d.vect.area with a cat-rgb file option, and not with the catnum 
> > option that was in d.area. This means that for scripts like the 
> > d.area.class I posted last week, I will have to go through a 
> > temporary file which will hamper perfomance again... I guess all 
> > this will not be a problem with the new vector format, but for the 
> > time being, I liked the catnum option.
> 
> d.area's "catnum=" option just takes a list of categories, not
> category/colour pairs.

Well it does in the sense that you can list all the categories you want to plot and the color you 
want to plot them in...

> Also, there's a limit on the maximum length of a command line (or,
> more usually, of the combined size of the command line and the
> environment list). Passing the colours via the command line would
> limit the maximum number of categories which could be coloured.

I guess my own test examples were just too limited to explode the command line...as I said I 
only tried with 589 areas.

> Ideally, vector layers should probably have associated colour tables,
> as is the case for raster layers.

Well, this will be addressed by the new vector format, won't it ?
 
> As for efficiency, a version of d.area.class based upon d.vect.area
> would only need to create the legend file and call d.vect.area once,
> rather than having to call d.area once per colour.

I'm quite inexperienced in programming, but doesn't the writing to a file take much more time 
than calling a module ?

Thanks for your response !

Moritz