## NAME

r.resamp.stats - Resamples raster map layers to a coarser grid using aggregation.

## KEYWORDS

raster, resample, univariate statistics, aggregation

## SYNOPSIS

r.resamp.stats
r.resamp.stats --help
r.resamp.stats [-nw] input=name output=name [method=string] [quantile=float] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

### Flags:

-n
  Propagate NULLs
-w
  Weight according to area (slower)
--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
output=name [required]
  Name for output raster map
method=string
  Aggregation method
  Options: average, median, mode, minimum, maximum, range, quart1, quart3, perc90, sum, variance, stddev, quantile, count, diversity
  Default: average
quantile=float
  Quantile to calculate for method=quantile
  Options: 0.0-1.0
  Default: 0.5

## DESCRIPTION

r.resamp.stats fills a grid cell (raster) matrix with aggregated values generated from a set of input layer data points.

Without the -w switch, the aggregate is computed over all of the input cells whose centers lie within the output cell.

With the -w switch, the aggregate uses the values from all input cells which intersect the output cell, weighted according to the proportion of the source cell which lies inside the output cell. This is slower, but produces a more accurate result.

## NOTES

Resampling modules (r.resample, r.resamp.stats, r.resamp.interp, r.resamp.rst) resample the map to match the current region settings.

The notion of weighting doesn't make any sense for the min and max aggregates. However, the -w flag still has significance in that, when multiple destination cells overlap a source cell, the source cell is included in the calculation of all of the destination cells.

## EXAMPLE

Resample elevation raster map to a lower resolution (from 6m to 20m; North Carolina sample dataset):

    g.region raster=el_D782_6m -p
    g.region res=20 -ap
    # from 6m to 20m: weighted resampling -w
    r.resamp.stats -w input=el_D782_6m output=el_D782_20m

Resampling of 6m DEM (left) to 20m DEM (right) with weighted resampling (subset)

## SEE ALSO

g.region, r.resample, r.resamp.rst, r.resamp.filter, r.resamp.interp, r.neighbors

Overview: Interpolation and Resampling in GRASS GIS

Examples how statistical functions are applied can be found in the r.neighbors module documentation.

## AUTHOR

Glynn Clements

## SOURCE CODE

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

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