[GRASS-dev] Re: [GRASS-user] Again on raster statistics

[Sören Gebbert]

Hi,
i can confirm this bug with the latest grass6.3-cvs version.

Using the test suite mapset i get the following result:

Mapset <testmapset> in Location <TestLocation> 
 
                                    GRASS 6.3.cvs > g.region -p res=200

GRASS 6.3.cvs > r.mapcalc "stat_test=col()*1.0"

GRASS 6.3.cvs > r.stats -npc input=stat_test nsteps=10
  100%
1-1.9 10  12.50%
1.9-2.8 10  12.50%
2.8-3.7 10  12.50%
3.7-4.6 10  12.50%
4.6-5.5 10  12.50%
5.5-6.4 10  12.50%
6.4-7.3 10  12.50%
7.3-8.2 10  12.50%
8.2-9.1 10  12.50%
9.1-10 10  12.50%

GRASS 6.3.cvs > r.stats -npc input=stat_test nsteps=2
  100%
1-5.5 90 102.27%
5.5-10 10  11.36%  <------------ ???
 
 
 
                                                      GRASS 6.3.cvs > 
r.stats -npc input=stat_test nsteps=3
  100%
1-4 50  57.47%
4-7 40  45.98%
7-10 10  11.49%  <------------ ???

I have created a bug report.

Best regards
Soeren

Luigi Ponti schrieb:
> Dear list,
> 
> I take up again a question I posted a couple of week ago with no aswer. 
> Maybe I am missing something trivial. If so, I would ask you to please 
> let me know.
> 
> In order to simulate a strange behaviour I ususally get when analyzing a 
> raster obtained via v.surf.idw, I have imported the following 
> sample_raster (into a  Lambert Conformal Conic location with roughly the 
> extent of Italy) :
> 
> north: 1957791.56244761
> south: 764918.56244761
> east: 754857.88911685
> west: -279947.29662612
> rows: 10
> cols: 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 1 2 3 4 5 6 7 8 9 10
> 
> using the following command:
> 
> GRASS 6.1.cvs (EurLCC):~ > r.in.ascii -f input=sample_raster.txt 
> output=sample_raster title="This is a sample raster"
> 
> Then if I use r.stats with 9 steps I get:
> 
> GRASS 6.1.cvs (EurLCC):~ > r.stats -nap sample_raster nsteps=9
> r.stats:  100%
> 1-2 246878233266.702148  22.23%
> 2-3 122842792398.404068  11.06%
> 3-4 124035440868.291550  11.17%
> 4-5 122842792398.404068  11.06%
> 5-6 124035440868.291550  11.17%
> 6-7 122842792398.404068  11.06%
> 7-8 124035440868.291550  11.17%
> 8-9 122842792398.404068  11.06%
> 9-10 124035440868.291550  11.17%
> 
> But with 2 steps I get:
> 
> GRASS 6.1.cvs (EurLCC):~ > r.stats -nap sample_raster nsteps=2
> r.stats:  100%
> 1-5.5 1110355725439.734619 100.00%
> 5.5-10 124035440868.291550  11.17%
> 
> Which does not make a lot of sense to me: there is too much area in the 
> first half and too little in the second half.
> Any hints appreciated. Regards,
> 
> Luigi
> 
> 
> 
> 
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