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NAME

       r3.univar  - Calculates univariate statistics from the non-null cells of a 3D raster map.
       Statistics  include  number  of  cells  counted,  minimum  and maximum cell values, range,
       arithmetic mean, population variance, standard deviation, coefficient  of  variation,  and
       sum.

KEYWORDS

       raster3d, statistics, univariate statistics

SYNOPSIS

       r3.univar
       r3.univar --help
       r3.univar  [-get]  map=name  [zones=name]   [output=name]   [percentile=float[,float,...]]
       [separator=character]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -g
           Print the stats in shell script style

       -e
           Calculate extended statistics

       -t
           Table output format instead of standard output format

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name [required]
           Name of 3D raster map

       zones=name
           3D Raster map used for zoning, must be of type CELL

       output=name
           Name for output file (if omitted or "-" output to stdout)

       percentile=float[,float,...]
           Percentile to calculate (requires extended statistics flag)
           Options: 0-100
           Default: 90

       separator=character
           Field separator
           Special characters: pipe, comma, space, tab, newline
           Default: pipe

DESCRIPTION

       r3.univar calculates the univariate statistics for a 3D raster  map.   This  includes  the
       number  of  cells  counted,  minimum  and  maximum  cell  values,  range, arithmetic mean,
       population variance, standard deviation, coefficient of variation, and sum. Statistics are
       calculated  separately  for every category/zone found in the zones input map if given.  If
       the -e extended statistics flag is given the 1st quartile, median, 3rd quartile, and given
       percentile  are calculated.  If the -g flag is given the results are presented in a format
       suitable for use in a shell script.  If the -t flag is given the results are presented  in
       tabular format with the given field separator. The table can immediately be converted to a
       vector attribute table which can then be linked to a vector,  e.g.  the  vector  that  was
       rasterized to create the zones input raster.

NOTES

       As  with most GRASS raster3d modules, r3.univar operates on the voxel array defined by the
       current 3d region settings, not the original extent and resolution of the input  map.  See
       g.region.

       This module can use large amounts of system memory when the -e extended statistics flag is
       used with a very large region setting. If the region is too large the module  should  exit
       gracefully  with  a  memory allocation error. Basic statistics can be calculated using any
       size input region.

EXAMPLE

       Computing univariate statistics of a 3D raster with randomly generated values:
       # define volume
       g.region n=10 s=0 w=0 e=10 b=0 t=10 res=1 res3=1 -p3
       # generate random map
       r3.mapcalc "random_0_1 = rand(0., 1)" -s
       # compute univariate statistics, along with extended statistics
       r3.univar -e map=random_0_1 percentile=98
        100%
       total null and non-null cells: 1000
       total null cells: 0
       Of the non-null cells:
       ----------------------
       n: 1000
       minimum: 0.00053905
       maximum: 0.998322
       range: 0.997783
       mean: 0.513676
       mean of absolute values: 0.513676
       standard deviation: 0.289969
       variance: 0.0840821
       variation coefficient: 56.4498 %
       sum: 513.676463040334
       1st quartile: 0.257654
       median (even number of cells): 0.524313
       3rd quartile: 0.763637
       98th percentile: 0.982924
       # script style output, along with extended statistics
       r3.univar -ge map=random_0_1 percentile=98
       n=1000
       null_cells=0
       cells=1000
       min=0.000539049520323687
       max=0.998322037540536
       range=0.997782988020212
       mean=0.513676463040334
       mean_of_abs=0.513676463040334
       stddev=0.289969154194666
       variance=0.0840821103843701
       coeff_var=56.4497646005434
       sum=513.676463040334
       first_quartile=0.257654
       median=0.524313
       third_quartile=0.763637
       percentile_98=0.982924

TODO

       To be implemented mode, skewness, kurtosis.

SEE ALSO

        g.region, r.univar, r.mode, r.quantile, r.series, r3.stats,  r.statistics,  v.rast.stats,
       v.univar

AUTHORS

       Soeren Gebbert
       Code is based on r.univar from
       Hamish Bowman, Otago University, New Zealand
       and Martin Landa
       Zonal loop by Markus Metz

       Last changed: $Date: 2016-05-03 19:09:18 +0200 (Tue, 03 May 2016) $

SOURCE CODE

       Available at: r3.univar source code (history)

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