t.rast.neighbors - GRASS manual
Author: GRASS Development Team
Description: t.rast.neighbors: Performs a neighborhood analysis for each map in a space time raster dataset.
Keywords: temporal, aggregation, raster, time

## NAME

t.rast.neighbors - Performs a neighborhood analysis for each map in a space time raster dataset.

## KEYWORDS

temporal, aggregation, raster, time

## SYNOPSIS

t.rast.neighbors
t.rast.neighbors --help
t.rast.neighbors [-cenr] input=name output=name [where=sql_query] [region_relation=string] [selection=name] [size=integer] method=string [weighting_function=string] [weighting_factor=float] [weight=name] [quantile=float[,float,...]] basename=string [suffix=name] [semantic_labels=string] [nprocs=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

### Flags:

-c
  Use circular neighborhood
-e
  Extend existing space time raster dataset
-n
  Register Null maps
-r
  Ignore the current region settings and use the raster map regions
--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 the input space time raster dataset
output=name [required]
  Name of the output space time raster dataset
where=sql_query
  WHERE conditions of SQL statement without 'where' keyword used in the temporal GIS framework
  Example: start_time > '2001-01-01 12:30:00'
region_relation=string
  Process only maps with this spatial relation to the current computational region
  Options: overlaps, contains, is_contained
selection=name
  Name of an input raster map to select the cells which should be processed
size=integer
  Neighborhood size
  Default: 3
method=string [required]
  Aggregate operation to be performed on the raster maps
  Options: average, median, mode, minimum, maximum, range, stddev, sum, count, variance, diversity, interspersion, quart1, quart3, perc90, quantile
  Default: average
weighting_function=string
  Weighting function
  Options: none, gaussian, exponential, file
  Default: none
  none: No weighting
  gaussian: Gaussian weighting function
  exponential: Exponential weighting function
  file: File with a custom weighting matrix
weighting_factor=float
  Factor used in the selected weighting function (ignored for weighting_function=none and file)
weight=name
  Text file containing weights
quantile=float[,float,...]
  Quantile to calculate for method=quantile
  Options: 0.0-1.0
basename=string [required]
  Basename of the new generated output maps
  A numerical suffix separated by an underscore will be attached to create a unique identifier
suffix=name
  Suffix to add at basename: set 'gran' for granularity, 'time' for the full time format, 'num' for numerical suffix with a specific number of digits (default %%05)
  Default: gran
semantic_labels=string
  Set semantic labels
  Options: input, method
  Default: input
  input: copy semantic labels from input to output
  method: append method name to input label if existing, otherwise use method name
nprocs=integer
  Number of r.neighbor processes to run in parallel
  Default: 1

## DESCRIPTION

t.rast.neighbors performs r.neighbors computations on the maps of a space time raster dataset (STRDS). This module supports the options that are available in r.neighbors.

The user must provide an input and an output space time raster dataset and the basename of the resulting raster maps. The resulting STRDS will have the same temporal resolution as the input dataset. With the -e flag, resulting maps can be registered in an existing STRDS, that e.g. may have been created with a previous run of t.rast.neighbors. All maps will be processed using the current region settings unless the -r flag is selected. In the latter case, the computaional region is set to each raster map selected from the input STRDS.

The user can select a subset of the input space time raster dataset for processing using a SQL WHERE statement or using the region_relation for spatial selection of raster maps. For the spatial map selection the current computational region is used, even when the -r flag is given. The number of CPU's to be used for parallel processing can be specified with the nprocs option to speedup the computation on multi-core system.

Semantic labels are needed to relate output raster maps to input raster maps. E.g. with method=stddev, the user needs to know the spatial extent, the time stamp and the semantic label to determine which stddev map corresponds to which input map.

## EXAMPLE

To smooth the maps contained in a space time dataset run:

    t.rast.neighbors input=tempmean_monthly output=smooth_tempmean_monthly \
                     basename=tmean_smooth size=5 method=average nprocs=4

    # show some info about the new space time dataset
    t.info smooth_tempmean_monthly
     +-------------------- Space Time Raster Dataset -----------------------------+
     |                                                                            |
     +-------------------- Basic information -------------------------------------+
     | Id: ........................ smooth_tempmean_monthly@climate_2000_2012
     | Name: ...................... smooth_tempmean_monthly
     | Mapset: .................... climate_2000_2012
     | Creator: ................... lucadelu
     | Temporal type: ............. absolute
     | Creation time: ............. 2014-11-27 11:41:36.444579
     | Modification time:.......... 2014-11-27 11:41:39.978232
     | Semantic type:.............. mean
     +-------------------- Absolute time -----------------------------------------+
     | Start time:................. 2009-01-01 00:00:00
     | End time:................... 2013-01-01 00:00:00
     | Granularity:................ 1 month
     | Temporal type of maps:...... interval
     +-------------------- Spatial extent ----------------------------------------+
     | North:...................... 320000.0
     | South:...................... 10000.0
     | East:.. .................... 935000.0
     | West:....................... 120000.0
     | Top:........................ 0.0
     | Bottom:..................... 0.0
     +-------------------- Metadata information ----------------------------------+
     | Raster register table:...... raster_map_register_ea1c9a83524e41a784d72744b08c6107
     | North-South resolution min:. 500.0
     | North-South resolution max:. 500.0
     | East-west resolution min:... 500.0
     | East-west resolution max:... 500.0
     | Minimum value min:.......... -6.428905
     | Minimum value max:.......... 18.867296
     | Maximum value min:.......... 4.247691
     | Maximum value max:.......... 28.767953
     | Aggregation type:........... None
     | Number of registered maps:.. 48
     |
     | Title:
     | Monthly precipitation
     | Description:
     | Dataset with monthly precipitation
     | Command history:
     | # 2014-11-27 11:41:36
     | t.rast.neighbors input="tempmean_monthly"
     |     output="smooth_tempmean_monthly" basename="tmean_smooth" size="5"
     |     method="average" nprocs="4"
     |
     +----------------------------------------------------------------------------+

    # now compare the values between the original and the smoothed dataset

    t.rast.list input=smooth_tempmean_monthly columns=name,start_time,min,max
    name|start_time|min|max
    tmean_smooth_1|2009-01-01 00:00:00|-3.361714|7.409861
    tmean_smooth_2|2009-02-01 00:00:00|-1.820261|7.986794
    tmean_smooth_3|2009-03-01 00:00:00|2.912971|11.799684
    ...
    tmean_smooth_46|2012-10-01 00:00:00|9.38767|18.709297
    tmean_smooth_47|2012-11-01 00:00:00|1.785653|10.911189
    tmean_smooth_48|2012-12-01 00:00:00|1.784212|11.983857

    t.rast.list input=tempmean_monthly columns=name,start_time,min,max
    name|start_time|min|max
    2009_01_tempmean|2009-01-01 00:00:00|-3.380823|7.426054
    2009_02_tempmean|2009-02-01 00:00:00|-1.820261|8.006386
    2009_03_tempmean|2009-03-01 00:00:00|2.656992|11.819274
    ...
    2012_10_tempmean|2012-10-01 00:00:00|9.070884|18.709297
    2012_11_tempmean|2012-11-01 00:00:00|1.785653|10.911189
    2012_12_tempmean|2012-12-01 00:00:00|1.761019|11.983857

## SEE ALSO

r.neighbors, t.rast.aggregate.ds, t.rast.extract, t.info, g.region, r.mask

## AUTHOR

Sören Gebbert, Thünen Institute of Climate-Smart Agriculture

## SOURCE CODE

Available at: t.rast.neighbors source code (history)

Accessed: Monday May 11 17:55:48 2026

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