Ubuntu Manpage: r.statistics - Calculates category or object oriented statistics.

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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

AUTHOR

       Martin Schroeder, Geographisches Institut Heidelberg, Germany

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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       © 2003-2013 GRASS Development Team