r.statistics

## 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
         .
         .
         .

To transfer the values stored as category labels into cell values, r.mapcalc can be used ('@' operator).

## 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