r3.stats(1)

NAME
r3.stats

DESCRIPTION
r3.stats calculates volume statistics for raster3D maps. Volumes are created on base of value subranges or groups of equal values. The default number of subranges is 20 and can vary from 1 to infinite. Larger subranges will result in larger memory consumption. The volumes are calculated in qubic meters. Null values are marked with "*". If the flag -e is set, the number of subrange will be ignored.

NOTES
As with most GRASS raster3D modules, r3.stats operates on the cell array defined by the current 3D region settings, not the original extent and resolution of the input map. See g.region.

The region setting will not effect the memory consumption of this module. The number of subranges in case of value range calculation or the number of equal value groups effect the memory consumption and the calculation time. You can expect a huge time consumption to calculate the equal value groups (flag -e) if you use large region settings + maps which have many equal value groups (> 100000).

EXAMPLES

  Lausanne FOSS4G 2006 3D demo dataset example
The 3D raster map geology has three values. Each value represents a specific geological layer, clay = 1, sand = 2 and bedrock = 3. To calculate the volume of each geological layer, we can use the flag -e to group equal values into single volumes. r3.stats geology -e will produce the following output:
  num | value | volume | perc | count
      1 1.000000 300822000.000 50.13700 50137
      2 2.000000 101400000.000 16.90000 16900
      3 3.000000 197778000.000 32.96300 32963
      4 * 0.000 0.00000 0
Number of groups with equal values: 3
Sum of non Null cells:
        Volume = 600000000.000
        Percentage = 100.000
        Count = 100000
Sum of all cells:
        Volume = 600000000.000
        Percentage = 100.000
        Count = 100000

  Generic example
#create a small 3D region
g.region n=1000 s=0 e=2000 w=0 t=300 b=0 res3=100
#create a raster3D map with row() and null values
r3.mapcalc "volmap = if(row() == 5, null(), row())"
#run r3.stats with a subrange of 10
r3.stats input=volmap nsteps=10
#the result should look like this
 num | minimum <= value | value < maximum | volume | perc | cell count
      1 1.000000000 1.900000000 60000000.000 10.00000 60
      2 1.900000000 2.800000000 60000000.000 10.00000 60
      3 2.800000000 3.700000000 60000000.000 10.00000 60
      4 3.700000000 4.600000000 60000000.000 10.00000 60
      5 4.600000000 5.500000000 0.000 0.00000 0
      6 5.500000000 6.400000000 60000000.000 10.00000 60
      7 6.400000000 7.300000000 60000000.000 10.00000 60
      8 7.300000000 8.200000000 60000000.000 10.00000 60
      9 8.200000000 9.100000000 60000000.000 10.00000 60
     10 9.100000000 10.000000001 60000000.000 10.00000 60
     11 * * 60000000.000 10.00000 60
Sum of non Null cells:
        Volume = 540000000.000
        Percentage = 90.000
        Cell count = 540
Sum of all cells:
        Volume = 600000000.000
        Percentage = 100.000
        Cell count = 600

SEE ALSO
g.region
r3.univar
r.stats
r.statistics
v.univar

AUTHORS
Soeren Gebbert

Last changed: $Date: 2011-03-18 10:31:26 +0100 (Fri, 18 Mar 2011) $

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