
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,average,mode,median,avedev,stddev,variance,skewness,kurtosis,min,max,sum
- output=name
- Resultant raster map
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):
- 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 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.
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
SEE ALSO
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: 2010-01-25 10:28:36 -0800 (Mon, 25 Jan 2010) $
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