## DESCRIPTION

The purpose of t.rast.extract is to extract a subset of a space time raster dataset and to store that subset in a different space time raster dataset. The where condition is used to select the subset. In addition a r.mapcalc sub-expression can be specified that performs operations on all maps of the selected subset. In this expression the name of the input space time raster dataset can be used as simple map name. Other STRDS than the input STRDS can not be specified, but any raster map. In case a r.mapcalc sub-expression is defined, the base name of the resulting raster maps must be specified. The r.mapcalc expression can be used to select maps as well, since by default resulting empty maps are not registered in the output space time raster dataset and removed after processing. The number of parallel GRASS GIS processes can be specified to speed up the processing.

If no r.mapcalc expression is defined, the selected maps are simply registered in the new created output space time raster dataset to avoid data duplication.

## NOTES

The r.mapcalc sub-expression should not contain the left side `"map ="` of a full r.mapcalc expression, only the right side, eg.:

    t.rast.extract input=tempmean_monthly where="start_time > '2010-01-05'" \
                   output=selected_tempmean_monthly basename=new_tmean_month \
                   expression="if(tempmean_monthly < 0, null(), tempmean_monthly)"

## EXAMPLE

    t.rast.extract input=tempmean_monthly output=tempmean_monthly_later_2012 \
                   where="start_time >= '2012-01-01'"

    t.rast.list tempmean_monthly_later_2012
    name|mapset|start_time|end_time
    2012_01_tempmean|climate_2000_2012|2012-01-01 00:00:00|2012-02-01 00:00:00
    2012_02_tempmean|climate_2000_2012|2012-02-01 00:00:00|2012-03-01 00:00:00
    2012_03_tempmean|climate_2000_2012|2012-03-01 00:00:00|2012-04-01 00:00:00
    2012_04_tempmean|climate_2000_2012|2012-04-01 00:00:00|2012-05-01 00:00:00
    2012_05_tempmean|climate_2000_2012|2012-05-01 00:00:00|2012-06-01 00:00:00
    2012_06_tempmean|climate_2000_2012|2012-06-01 00:00:00|2012-07-01 00:00:00
    2012_07_tempmean|climate_2000_2012|2012-07-01 00:00:00|2012-08-01 00:00:00
    2012_08_tempmean|climate_2000_2012|2012-08-01 00:00:00|2012-09-01 00:00:00
    2012_09_tempmean|climate_2000_2012|2012-09-01 00:00:00|2012-10-01 00:00:00
    2012_10_tempmean|climate_2000_2012|2012-10-01 00:00:00|2012-11-01 00:00:00
    2012_11_tempmean|climate_2000_2012|2012-11-01 00:00:00|2012-12-01 00:00:00
    2012_12_tempmean|climate_2000_2012|2012-12-01 00:00:00|2013-01-01 00:00:00

## SEE ALSO

t.create, t.info

## AUTHOR

Sören Gebbert, Thünen Institute of Climate-Smart Agriculture

Last changed: $Date: 2015-09-22 10:10:38 +0200 (Tue, 22 Sep 2015) $