r.statisticsgrass - Online in the Cloud

PROGRAM:

NAME

r.statistics - Calculates category or object oriented statistics.

KEYWORDS

raster, statistics, zonal statistics

SYNOPSIS

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

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

--overwrite
Allow output files to overwrite existing files

--help
Print usage summary

--verbose
Verbose module output

--quiet
Quiet module output

--ui
Force launching GUI dialog

Parameters:
base=name [required]
Name of base raster map

cover=name [required]
Name of cover raster map

method=string [required]
Method of object-based statistic
Options: diversity, average, mode, median, avedev, stddev, variance, skewness,
kurtosis, min, max, sum
diversity: Diversity of values in specified objects in %%
average: Average of values in specified objects
mode: Mode of values in specified objects
median: Median of values in specified objects
avedev: Average deviation of values in specified objects
stddev: Standard deviation of values in specified objects
variance: Variance of values in specified objects
skewness: Skewnes of values in specified objects
kurtosis: Kurtosis of values in specified objects
min: Minimum of values in specified objects
max: Maximum of values in specified objects
sum: Sum of values in specified objects

output=name [required]
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 integer 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

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