[GRASSLIST:9544] Re: modifications to v.rast.stats

[Markus Neteler]

Matthew,

today I have fixed a couple of things in v.rast.stats.
The r.univar trick is implemented as well.

Would you mind to integrate the suggested v.extract trick
into the current CVS version?

Thanks

 markus

On Wed, Nov 23, 2005 at 12:06:52PM -0800, Matthew Perry wrote:
> Hey folks,
> 
>   In order to speed up the v.rast.stats script, I've made some changes
> that might be of interest. I'm relatively new to GRASS so let me know
> if there is a better way to do this...
> 
> The main issue was, instead of running r.univar multiple times for
> each statistic, I run it once, save to a temp file, then cat the
> results for each statistic...
> 
> $ diff v.rast.stats v.rast.stats.old
> 
> <  # Run once only and save to temp file
> <  r.univar -g $RASTER > .${TMPNAME}.univar
> <  n=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f1`
> <  min=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f2`
> <  max=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f3`
> <  range=`cat .${TMPNAME}.univar |  cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f4`
> <  mean=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f5`
> <  stddev=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f6`
> <  variance=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' |
> cut -d' ' -f7`
> <  cf_var=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f8`
> <  sum=`cat .${TMPNAME}.univar | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f9`
> ---
> >  n=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f1`
> >  min=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f2`
> >  max=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f3`
> >  range=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f4`
> >  mean=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f5`
> >  stddev=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f6`
> >  variance=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f7`
> >  cf_var=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f8`
> >  sum=`r.univar -g $RASTER | cut -d'=' -f2 | tr '\n' ' ' | cut -d' ' -f9`
> 
> 
> Of course, in case the user breaks out of the script, we have to add
> this to the cleanup() function:
> 
> <  rm .${TMPNAME}.univar
> 
> 
> I also noticed that it runs the whole analysis at the full extents of
> the raster map. Since we're looping through categories and creating a
> raster mask, we only need to be worried about the extents of that
> particular vector category.
> 
> I'm not sure if this is the most elegant way to solve the issue but I
> create a temp vector map of the particular category and set the region
> to this vector. This speeds up the creation of the raster mask for
> cases when you have very large rasters and lots of smaller polygons.
> 
> <
> <  #  Extract the current category and set region
> <  v.extract input=$VECTOR output=${VECTOR}_CAT${i} list=$i >
> /dev/null 2> /dev/null
> <  g.region vect=${VECTOR}_CAT${i} > /dev/null 2> /dev/null
> <
> <  # Make certain we are using the proper resolution
> <  g.region nsres=$NSRES ewres=$EWRES -ap > /dev/null
> <
> <  #Remove temporary vector
> <  g.remove vect=${VECTOR}_CAT${i} > /dev/null 2> /dev/null
> <
> <  # generate mask .....
> 
>  The one problem is that if a certain vector category extent is
> smaller than the current cellsize, g.region fails. Any ideas on a more
> elegant way?
> 
> For the record, this reduced operation time on my project from about
> 240 seconds per vector category to an average of 9 seconds.
> 
> --
> Matt Perry
> National Center for Ecological Analysis and Synthesis
> University of California, Santa Barbara
> perrygeo at gmail.com
> 

-- 
Markus Neteler     <neteler itc it>       http://mpa.itc.it
ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
Via Sommarive, 18        -       38050 Povo (Trento), Italy