Details Ticket 4917


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Serial Number 4917
Subject ps.map: legend of vpoints sizes
Area grass6
Queue grass
Requestors mlennert@club.worldonline.be
Owner none
Status open
Last User Contact Never contacted
Current Priority 30
Final Priority 70
Due No date assigned
Last Action Mon Aug 28 06:37:19 2006 (2 yr ago)
Created Fri Jul 28 15:56:04 2006 (2 yr ago)

Transaction History Ticket 4917


Fri, Jul 28 2006 15:56:04    Request created by guest  
Subject: ps.map: legend of vpoints sizes

Platform: GNU/Linux/x86
grass obtained from: CVS
grass binary for platform: Compiled from Sources
GRASS Version: cvs_head_20060724

The sizecol option of the vpoints command in ps.map allows to make the point
symbols' size vary with the value of an attribute column.
It would be great if there was some sort of legend command which would allow
to create a legend of these circle sizes. It would mean taking the icon and scale
from the vpoints command, applying the desired legend values and positioning
this legend somewhere, plus the normal text options for the legend text.

Moritz
Mon, Jul 31 2006 12:20:20    Mail sent by mlennert@club.worldonline.be  
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Date Mon, 31 Jul 2006 12:20:22 +0200
From Moritz Lennert <mlennert@club.worldonline.be>
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To Request Tracker <grass-bugs@intevation.de>
Cc grass-dev@grass.itc.it, Hamish <hamish_nospam@yahoo.com>
Subject Re: [GRASS-dev] [bug #4917] (grass) ps.map: legend of vpoints sizes
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Request Tracker wrote:
> this bug's URL: http://intevation.de/rt/webrt?serial_num=4917 
> -------------------------------------------------------------------------
> 
> 
> Subject: ps.map: legend of vpoints sizes
> 
> Platform: GNU/Linux/x86 grass obtained from: CVS grass binary for
> platform: Compiled from Sources GRASS Version: cvs_head_20060724
> 
> The sizecol option of the vpoints command in ps.map allows to make
> the point symbols' size vary with the value of an attribute column. 
> It would be great if there was some sort of legend command which
> would allow to create a legend of these circle sizes. It would mean
> taking the icon and scale from the vpoints command, applying the
> desired legend values and positioning this legend somewhere, plus the
> normal text options for the legend text.
> 

Still thinking of how to implement this best, I am thinking along the 
following lines:

- add an lvalues option to the vpoints command which would take the 
values for which one would like to draw symbols in the legend:

i.e.: lvalues 500,2500,10000

- modify lines 216-216 in ps/ps.map/ps_vlegend.c so that it draws as 
many symbols as needed

Does this general idea sound reasonable, or should such a legend be 
drawn separately from the vlegend ?

Issues that need to be solved:

- should the symbols be drawn inside each other (easy for circles, but 
maybe not for others) ?
- if they are not inside each other should they be next to each other or 
one above the other
- if the latter, then each should probably be registered seperately in 
vec[][] / nvec[]
- how to deal with the text: draw lines from symbols to (small) text, 
write values next to each other in the same order as the symbols, e.g.: 
o O 10 50

Hamish, as you are the ps.map expert, what do you think ?

Moritz


Mon, Aug 28 2006 06:23:26    Area changed to grass6 by hbowman  
Mon, Aug 28 2006 06:37:19    Comments added by hbowman  
Hi,

I've changed this wish to a bug as it is broken to offer symbol sizing but not
allow the user to reference what those sizes mean. (this is my fault, but I'm
not taking ownership of the bug as I don't have much time to work on it right
now. Maybe someone else can take it up?)

My idea for how it should look:

just like multiple vpoints symbol listings in the vector legend, symbol on the
left at the given size with text on the right. multiple circles in powers of
10 (or whatever), one per line, lines spaced as needed. We should make an
effort to calculate the sizes used automatically from the data range, with a
custom-override setting (e.g. default 5 entries, just like ps.map's floating
point colorbar [reuse that code]). Tapping into or extending the existing
vlegend C array would be best (if that doesn't require too many changes).

Using concentric circles is an interesting idea, but as they get smaller than
1cm labeling them gets tricky/messy. Same if the symbol used isn't a circle.
Hamish
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