[GRASS-user] displaying many thematic maps from one vector dataset

[Moritz Lennert]

On 04/04/09 01:13, Vishal Mehta wrote:
> A couple of strange behaviors with a test vector dataset whose columns 
> are population projections every 5 years:
> I ran the following script below but:
> 1. I see it working ok on the x0 monitor; but the output png files are 
> all blank..
> 2. and i get messages while the script is running that include 
> 'segmentation fault' but not on EVERY iteration of the loop..

I've seen this problem before, but not with fixed class breaks, but was 
not able to find its cause. The fact that you see it as well with fixed 
class breaks is already an interesting information that should help find 
out what is wrong. Note that this module has seen _very_ little testing 
up to now (if not none except mine).

And so you say that this only happens with PNG output (are you using 
d.mon PNG ?), but not on the x-monitors ?

Moritz


> 
> ---------------------script-------
> #!/bin/bash
> #generate 5yr interval thematic pngs of low series PPIC population 
> projectiosn
> yr=2010
> while [ $yr -lt 2105 ] ; do
> 
> #actions here
> echo "yr is $yr "
> 
> d.thematic.area map=CountyPop column=pc$yr breaks=20,40,60 
> colors=cyan,blue,yellow,red
> d.out.file output=pop$yr format=png
> #
> yr=$((yr+5))
> done
> ------------------------messages while running above script-----
> 
> ---
> yr is 2020
> Segmentation fault
> Saving display from Monitor: [x0] to <pop2020.png>.
> Image size [640 x 480]
> Screen export complete. (writing the file may take a small amount of time)
> Image crop [523 x 480]
> Done.
> yr is 2025
> Segmentation fault
> Saving display from Monitor: [x0] to <pop2025.png>.
> Image size [640 x 480]
> Screen export complete. (writing the file may take a small amount of time)
> Image crop [523 x 480]
> Done.
> yr is 2030
> Segmentation fault
> Saving display from Monitor: [x0] to <pop2030.png>.
> Image size [640 x 480]
> Screen export complete. (writing the file may take a small amount of time)
> Image crop [523 x 480]
> Done.
> yr is 2035
> Saving display from Monitor: [x0] to <pop2035.png>.
> Image size [640 x 480]
> Screen export complete. (writing the file may take a small amount of time)
> Image crop [523 x 480]
> Done.
> yr is 2040
> Saving display from Monitor: [x0] to <pop2040.png>.
> Image size [640 x 480]
> Screen export complete. (writing the file may take a small amount of time)
> Image crop [523 x 480]
> Done.
> yr is 2045
> Saving display from Monitor: [x0] to <pop2045.png>.
> Image size [640 x 480]
> Screen export complete. (writing the file may take a small amount of time)
> Image crop [523 x 480]
> Done.
> ------
> 
> On Thu, Apr 2, 2009 at 11:54 PM, Moritz Lennert 
> <mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>> wrote:
> 
>     On 03/04/09 00:23, Vishal Mehta wrote:
> 
>         Hello all,
> 
>         I am better at GRASS raster capabilities than with GRASS vector
>         handling, so I am writing to get your help.
> 
>         What I want to do is this:
>         1. I will have one vector dataset of watersheds. Each record is
>         a polygon, an individual watershed. There are, apart from the
>         usual cat fields, 52 attribute columns. Each attribute column is
>         modeled weekly snow depth.
> 
>         2. I need to automate the display and export to png of 52
>         thematic images - one for each week/column - keeping the color
>         scheme constant throughout. Then all of the images will be
>         packaged into a kml animation.
> 
>         I know how to do the above starting from a stack of GRASS
>         rasters, but am not quickly getting a handle on displaying GRASS
>         vectors consistently. I've tried d.vect and d.vect.thematic. I
>         havent tried d.thematic.area yet.
> 
>         The main issues are that I dont know:
>         - how to assign a constant color scheme  to each map (that spans
>         the min and max of all columns); i guess i was looking for
>         something as simple as setting color rules like with raster data.
> 
> 
>     If you want constant class breaks, i.e. the same class number and
>     amplitudes linked to the same colors, then you can just manually
>     provide breaks and colors in d.thematic.area.
> 
> 
>          - how to refer to each attribute column by column number in a
>         loop (d.vect.thematic and d.thematic.area  seem to need column
>         name as attribute)
> 
> 
>     (assuming you are in a *nix environment with a shell):
>     for col in `v.info <http://v.info> -c MapName`; do d.thematic.area
>     .... column=$col; done
>     (note the backticks around the v.info <http://v.info> command))
> 
>     Moritz
> 
> 
> 
> 
> -- 
> Vishal K. Mehta, PhD
> Scientist
> Stockholm Environment Institute - US
> 133 D St Suite F
> Davis CA 95616
> www.sei-us.org <http://www.sei-us.org>