NAME
r.statistics - Category or object oriented statistics.
KEYWORDS
raster
SYNOPSIS
r.statistics
r.statistics help
r.statistics [-c] base=string cover=string method=string [output=string] [--overwrite]
Flags:
- -c
- Cover values extracted from the category labels of the cover map
- --overwrite
- Force overwrite of output files
Parameters:
- base=string
- Base raster map
- cover=string
- Cover raster map
- method=string
- Method of object-based statistic
- Options: distribution,average,mode,median,avedev,stddev,variance,skewness,kurtosis,min,max,sum
- output=string
- Resultant raster map (not used with 'distribution')
DESCRIPTION
r.statistics is a tool, where different class, resp. object
oriented statistical analysis methods are possible.
The 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 for areas with data of the
covering-layers which belong in the base-layer o the same category.
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.
The output-layer is a reclassified version of the base-layer with identical
category values. The results of the calculations are stored in the category
labels of the output-layer.
The described output is valid for all calculations with exception of
distribution. Here the output is given to stdout. A file name eventually
specified will be ignored. The result will be a table with three columns.
In the 1. column are the category values of the base-layer (a), in the 2.
column the associated value of the cover-Layers (b) and in the 3. column the
percentage of b from a. Example:
1 124 23
1 201 47
1 273 30
2 101 5
2 152 16
2 167 60
2 187 19
.
.
.
EXAMPLE
Calculation of average elevation of each field in the Spearfish region:
r.statistics base=fields cover=elevation.dem out=elevstats method=average
r.cats elevstats
r.mapcalc "fieldelev=@elevstats"
r.univar fieldelev
REMARK
The source code of average, mode and median was taken from some GRASS raster
modules.
BUGS
unkown
SEE ALSO
r.mode,
r.median,
r.average,
r.mapcalc,
r.neighbors
AUTHOR
Martin Schroeder, Geographisches Institut Heidelberg, Germany
Last changed: $Date: 2006/08/08 13:09:15 $
Main index - raster index - Full index