r.quantile(1)

NAME
r.quantile - Compute quantiles using two passes.

KEYWORDS
raster, algebra, statistics, percentile, quantile

SYNOPSIS
r.quantile
r.quantile --help
r.quantile [-r] input=name [quantiles=integer] [percentiles=float[,float,...]] [bins=integer] [file=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

  Flags:

-r
    Generate recode rules based on quantile-defined intervals

--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:

input=name [required]
    Name of input raster map

quantiles=integer
    Number of quantiles
    Default: 4

percentiles=float[,float,...]
    List of percentiles

bins=integer
    Number of bins to use
    Default: 1000000

file=name
    Name for output file (if omitted or "-" output to stdout)

DESCRIPTION
r.quantile computes quantiles in a manner suitable for use with large amounts of data. It is using two passes.

NOTES
Quantiles are calculated following algorithm 7 from Hyndman and Fan (1996), which is also the default in R and numpy.

EXAMPLE
Calculation of elevation quantiles (printed to standard-out):

g.region raster=elevation -p
r.quantile input=elevation percentiles=0.1,1,10,25,50,75,90,99,99.9

The output of r.quantile can be used for quantile classification:

g.region raster=elevation -p
r.quantile elevation quantiles=5 -r --quiet | r.recode elevation \
           out=elev_quant5 rules=-

REFERENCES

    •   Hyndman and Fan (1996) Sample Quantiles in Statistical Packages, American Statistician. American Statistical Association. 50 (4): 361-365. DOI: 10.2307/2684934

    •   Engineering Statistics Handbook: Percentile, NIST

SEE ALSO
r.mode, r.quant, r.recode, r.series, r.stats, r.stats.quantile, r.stats.zonal, r.statistics, r.univar, v.rast.stats

AUTHORS
Glynn Clements
Markus Metz

SOURCE CODE

Available at: r.quantile source code (history)

Accessed: Wednesday Apr 10 11:17:53 2024

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