NAME

r.stats.quantile - Compute category quantiles using two passes.

KEYWORDS

raster, statistics, zonal statistics, percentile, quantile

SYNOPSIS

r.stats.quantile
r.stats.quantile --help
r.stats.quantile [-rpt] base=name cover=name [quantiles=integer] [percentiles=float[,float,...]] [bins=integer] [output=name[,name,...]] [file=name] [separator=character] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-r: Create reclass map with statistics as category labels
-p: Do not create output maps; just print statistics
-t: Print statistics in table format
--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
quantiles=integer: Number of quantiles
percentiles=float[,float,...]: List of percentiles
Default: 50
bins=integer: Number of bins to use
Default: 1000
output=name[,name,...]: Resultant raster map(s)
file=name: Name for output file (if omitted or "-" output to stdout)
separator=character: Field separator
Special characters: pipe, comma, space, tab, newline
Default: :

DESCRIPTION

r.stats.quantile is a tool to analyse exploratory statistics of a floating-point "cover layer" according to how it intersects with objects in a "base layer". It provides quantile calculations as selected "zonal statistics".

NOTES

r.stats.quantile is intended to be a partial replacement for r.statistics, with support for floating-point cover maps. It provides quantile calculations, which are absent from r.stats.zonal.

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

EXAMPLE

In this example, the raster polygon map zipcodes in the North Carolina sample dataset is used to calculate quantile raster statistics using the elevation raster map:

g.region raster=zipcodes -p
# print quantiles
r.stats.quantile base=zipcodes cover=elevation quantiles=3 -p
27511:0:33.333333:134.717392
27511:1:66.666667:143.985723
27513:0:33.333333:140.669993
27513:1:66.666667:146.279449
27518:0:33.333333:115.140101
27518:1:66.666667:129.893723
[...]
# write out percentile raster maps
r.stats.quantile base=zipcodes cover=elevation percentiles=25,50,75 \


  output=zipcodes_elev_q25,zipcodes_elev_q50,zipcodes_elev_q75

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

AUTHORS

Glynn Clements
Markus Metz

SOURCE CODE

Available at: r.stats.quantile source code (history)

Latest change: Tuesday Dec 17 20:17:20 2024 in commit: d962e90c026708a4815ea2b9f46c0e84c17de22d