r.resamp.stats - GRASS manual

NAME

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

KEYWORDS

raster, resample, univariate statistics, aggregation, parallel

SYNOPSIS

r.resamp.stats

r.resamp.stats --help

r.resamp.stats [-nw] input=name output=name [method=string] [quantile=float] [nprocs=integer] [memory=memory in MB] [--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
nprocs=integer: Number of threads for parallel computing; 0: use OpenMP default; >0: use nprocs; <0: use MAX-nprocs; Default: 0
memory=memory in MB: Maximum memory to be used (in MB); Cache size for raster rows; Default: 300

DESCRIPTION
NOTES
- PERFORMANCE
EXAMPLE
SEE ALSO
AUTHOR

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.

PERFORMANCE

By specifying the number of parallel processes with nprocs option, r.resamp.stats can run faster. See the benchmark script in the source code.

To reduce the memory requirements to minimum, set option memory to zero. To take advantage of the parallelization, GRASS needs to be compiled with OpenMP enabled.

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)

AUTHOR

Glynn Clements

SOURCE CODE

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

Latest change: Wednesday Sep 02 22:25:59 2026 in commit: ba172cdc5e8f3bd458e070d5098b7421a937f932