### r3.univar (1)

#### 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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2003-2017 GRASS Development Team, GRASS GIS 7.2.1 Reference Manual