Homepage > Man Pages > Category > General Commands
Homepage > Man Pages > Name > R

# r.statistics

## man page of r.statistics

### r.statistics: Calculates category or object oriented statistics.

```NAME
r.statistics  - Calculates category or object oriented statistics.

KEYWORDS
raster, statistics

SYNOPSIS
r.statistics
r.statistics help
r.statistics  [-c]  base=name  cover=name  method=string  [output=name]
[--overwrite]  [--verbose]  [--quiet]

Flags:
-c
Cover values extracted from the category labels of the cover map

--overwrite
Allow output files to overwrite existing files

--verbose
Verbose module output

--quiet
Quiet module output

Parameters:
base=name
Name of base raster map

cover=name
Name of cover raster map

method=string
Method of object-based statistic
Options:
diversity,distribution,average,mode,median,avedev,stddev,variance,skewness,kurtosis,min,max,sum

output=name
Resultant raster map (not used with 'distribution')

DESCRIPTION
r.statistics is a tool to analyse exploratory statistics  of  a  "cover
layer"  according  to how it intersects with objects in a "base layer".
A variety of standard statistical measures are possible (called  "zonal
statistics"  in  some GIS).  All cells in the base layer are considered
one object for the analysis.  For some  applications,  one  will  first
want  to  prepare  the  input data so that all areas of contiguous cell
category values in the base layer are uniquely identified, which can be
done with r.clump.
The available methods are the following (english - german):

distribution - Verteilung in Prozent

average - Durchschnitt

mode - Modalwert

median - Median

average deviation - Durchschnittliche Abweichung

standard deviation - Standardabweichung

variance - Varianz

skewness - Schiefe der Verteilung

kurtosis - Relative Abflachung (-) oder Zuspitzung (+)

minimum - Minimum

maximum - Maximum

sum - Summe
The  calculations  will  be performed on each area of data of the cover
layers which fall within each unique value, or category,  of  the  base
layer.

Setting  the  -c  flag the category lables of the covering raster layer
will be used.  This is nice to avoid the GRASS limitation  to  interger
in raster maps because using category values floating point numbers can
be stored.

All calculations except "distribution" create  an  output  layer.   The
output layer is a reclassified version of the base layer with identical
category values, but modified category labels  -  the  results  of  the
calculations are stored in the category labels of the output layer.

For  distributions,  the  output  is  printed  to  the  user  interface
(stdout).  If an output file name was specified, it  will  be  ignored.
The  result  will  be  a  text  table with three columns.  In the first
column are the category values of the base layer  (a),  in  the  second
column  the  associated value of the cover layers (b), and in the third
column the percentage of area in that  base  layer  category  (a)  that
falls into that row's value in the cover layer(b). Example:
1   124  23
1   201  47
1   273  30
2   101  5
2   152  16
2   167  60
2   187  19
.
.
.
So  for  the  first  line in the output above, we see that 23% of the
cells of the base layer category 1 have a value of  124  in  the  cover
layer.   To  transfer  the  values  stored as category labels into cell
values, r.mapcalc can be used ('@' operator).

EXAMPLES
Calculation of average elevation of each field in the Spearfish region:
r.statistics     base=fields     cover=elevation.dem      out=elevstats
method=average
r.category elevstats
r.mapcalc "fieldelev=@elevstats"
r.univar fieldelev

r.average, r.clump, r.mode, r.median, r.mapcalc, r.neighbors, r.univar
r.category

AUTHOR
Martin Schroeder, Geographisches Institut Heidelberg, Germany

Last changed: \$Date: 2008-05-23 18:57:25 +0200 (Fri, 23 May 2008) \$

Full index

(C) 2003-2010 GRASS Development Team

R.STATISTICS(1)
```