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: Thursday Aug 01 11:30:13 2024

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       © 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual