[GRASS5] New thematic mapper for GRASS 6

[Michael Barton]

Moritz,

Thanks for the info and testing. I'll quickly reply below.

Michael
______________________________
Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ  85287-2402
USA

voice: 480-965-6262; fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton


> From: Moritz Lennert <mlennert at club.worldonline.be>
> Reply-To: <mlennert at club.worldonline.be>
> Date: Wed, 11 May 2005 15:08:43 +0200 (CEST)
> To: Michael Barton <michael.barton at asu.edu>
> Cc: grass5 developers list <grass5 at grass.itc.it>
> Subject: Re: [GRASS5] New thematic mapper for GRASS 6
> 
> Michael,
> 
> On Wed, May 11, 2005 7:39, Michael Barton said:
>> I¹ve just finished a thematic mapper for vector maps in GRASS 6,
> d.vect.thematic, and am hoping that some of you can help test it.
> 
> 
> This is way cool !
> 
> I had been thinking about something like this for a while, but as always, I
> think too much and do too little ;-)
> 
> First superficial testing shows it works great, with just a few remarks:
> 
> - One problem I encounter sometimes (still trying to figure out the exact
> sequence leading to this) is the following error:
> 
> /usr/local/grass-6.1.cvs/scripts/d.vect.thematic: line 143: TMP1: Permission
> denied

I am using g.temp to generate a TMP file ID and create a TMP file to hold
data needed to calculate stats. This is actually taking place in v.univar.sh
and would be unnecessary if v.univar can be fixed/upgraded. I'm using the
format that is required for proper security in creating temporary files. I'm
guessing that there is a problem on your system in writing a file in the
appropriate locale. Is there possibly another TMP1 already created (by
another process) and in use in this area?

> 
> and then nothing is displayed as the file suppoed to contain the statistics is
> empty.

See above

> 
> 
> - The options available in the key "type" should be reduced to the only
> sensible ones (point, centroid, area) as the others don't seem to work (or I
> misunderstood something); also it might be useful to print a warning if the
> type of thematic map display is set to "graduated points" and the vector map
> type to "area" and vice versa. Currently the program runs, but nothing shows
> up.
> 

In fact, lines and boundaries should also display with graduated colors
here. So they do make sense. I haven't tested it with lines yet however.

> 
> - Concerning the legend: it would be good to have a precise indication of
> where one category ends and the other starts. At the moment, it prints
> something like
> 
> 1.000000-3.2725    5
> 3.2725-5.545    7
> 5.545-7.8175    9
> 7.8175-10.09    11

The algorithm specifies the range (given above) then looks for records > 1st
number and <= 2nd number. I understand what you are wanting to do, but not
sure how to do it. I'll see if I can figure out something as I refine this.


> 
> so if you have a value of 3.2725, you don't know in which category it is...
> If I understand the code correctly it is in the first category and the legend
> should therefore be:
> 
> 1.000000-3.2725    5
> 3.2726-5.545    7
> 
> 
> or some other way of saying that the range goes from minimum (exclusive) to
> maximum (inclusive).
> BTW the way, this raises the question of what happens if a feature has exactly
> the $min value of the first category ?

Right now it gets left out. But this I can change (I think).

> 
> 
> And just to prove once again that users are a terribly ungrateful bunch and
> always want more, here a few wishes:
> 
> - I think one useful addition would be the possibility to display the
> available columns, or, even better, to chose from a list of available columns.

I'd love to do this, but don't know how to program this in the existing
g.parser interface via shell scripting at the moment.

> 
> - It was very easy for me to very quickly create a new color scheme (here we
> use blue for low values and red for high values...) in the script. That's very
> useful for those of us who are not afraid of going into the code. But it would
> be interesting to see if there is a way to offer a color choser to chose the
> min and max color and to automatically calculate the intermediate values.
> Another great option would be to also be able to chose all the colors
> manually...

I'd also like a color chooser (kind of like in r.colors rules). I have an
idea of how this might be accomplished. I don't know if this would make it
harder (i.e., too complicated) or easier for most people to do.

I thought about a manual color chooser, but realized that by making a group
in the GIS Manager and duplicating a vector display line, there is already a
much better interface for doing this than I could do in a script.

> 
> Congrats Michael, this will make GRASS much usable for all the vector bunch
> out there !

Thanks for your input. It is indeed appreciated. I'm glad if it helps those
who are using vectors.

Now if someone could just figure out  how to re-write d.legend for vectors
also....

Michael

> 
> Moritz
>