## 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

## SEE ALSO

r.quantile, r.stats.zonal, r.statistics

## AUTHORS

Glynn Clements
Markus Metz