Focal Statistics

Draft: written, not yet checked by a person Operation · focal-statistics

Each cell gets a statistic (mean, sum, minimum, ...) of the cells in a window around it.

Pitfall. Cells near the edge have incomplete windows; engines use the partial window, return nodata, or pad.

About this operation
Also called	neighborhood statistics, moving window, mean filter, focal mean, r.neighbors
Group	`raster/neighborhood`
Checks	`raster.nodata`
Pitfalls	1 listed above
Columbus tool	Not stated
Notes	Not stated
Status	active
Broader	Not stated
Narrower	Not stated
Related	`zonal-statistics`

Parameters

Name	Type	Required	Default	Values	Note
`statistic`	enum	no	`mean`	`mean, sum, min, max, median, std`	Not stated
`size`	integer	no	`3`	Not stated	Window width in cells (an odd number).

Direction	Name	Type	Geometry	Note
Input	`raster`	raster	Not stated	Not stated
Output	`output`	raster	Not stated	Not stated

Engine	Tool	Parameters	Differences
`gdal`	`gdal raster neighbors`	`statistic` → `method` : mean = mean; sum = sum; min = min; max = max; median = median; std = stddev `size` → `size` `raster` → `input` `output` → `output`	kernel is required; equal (all weights 1) gives the plain window statistic. kernel gives other weights (a Gaussian, edge detection) or a custom matrix. Preset: `{"kernel":"equal"}`
`grass`	`r.neighbors`	`statistic` → `method` : mean = average; sum = sum; min = minimum; max = maximum; median = median; std = stddev `size` → `size` `raster` → `input` `output` → `output`	The c flag uses a circular window.
`terra`	`terra::focal`	`statistic` → `fun` : mean = mean; sum = sum; min = min; max = max; median = median; std = sd `size` → `w` `raster` → `x`	fun defaults to sum; w can also be a weights matrix.
`whiteboxtools`	`MeanFilter`	`statistic` always mean. Other filters are separate tools (MedianFilter, MaximumFilter, ...). `size` filterx and filtery: the window's width and height in cells. `raster` → `input` `output` → `output`	None noted
`xarray-spatial`	`xrspatial.focal.focal_stats`	`statistic` → `stats_funcs` : A list of statistic names. `size` kernel: an array, e.g. from xrspatial.convolution.circle_kernel or a square of ones. `raster` → `agg`	None noted