[GRASSLIST:10386] Re: how to determine percent of coverage

[Jonathan Greenberg]

Dylan:

	You can do this with starspan, actually -- if you have a raster map
that's 0 if not rain and 1 if rain, and a set of polys to constrain the
raster, just take the average value of the rasters per poly which will be =
% cover (e.g. if you have 5 0s and 5 1s, the average will be 0.5 = 50%).

	This help?
--j

--

Jonathan A. Greenberg, PhD
NRC Research Associate
NASA Ames Research Center
MS 242-4
Moffett Field, CA 94035-1000
Office: 650-604-5896
Cell: 415-794-5043
AIM: jgrn3007
MSN: jgrn3007 at hotmail.com

-----Original Message-----
From: owner-GRASSLIST at baylor.edu [mailto:owner-GRASSLIST at baylor.edu] On
Behalf Of Dylan Beaudette
Sent: Friday, February 17, 2006 5:06 PM
To: bfdi533 at cbacc-security3.mccombs.utexas.edu
Cc: GRASS user list
Subject: [GRASSLIST:10383] Re: how to determine percent of coverage

On Monday 13 February 2006 07:01 am, Ed Davison wrote:
> I have a radar map that I am loading into a lat/long mapset.  I have
> taken the original input and converted all cells of the raster to null
> where there is no real radar info.  So, what I am trying to do is to
> take an area, say a county, and run an analysis to determine what
> percent of the area has rain (any data other than null).  I do not want
> to sum all data but to get a percent of area with any value other than
> null.
>
> I think that I probably need to somehow get the area into a raster layer
> so it can be used as a mask (?) for anaylsis purposes.  Is that right?
>
> Then I will probably need to use something like r.mapcalc but cannot
> figure out how to do this, even after reading through the man page
> several times.
>
> Can anyone give me any pointers on this?
>
> Ed Davison

Hi,
check out:
r.report
r.stats

cheers,

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341