DESCRIPTION
This command creates a random sample of n% of the sites in a GRASS sites map. The current
process id (pid) and system time are used as seed for the random number generator.
If a raster map is specified, then only sites falling on non-NULL cells of that raster map
will be included in the sample.
The program will abort with an error message, if the number of valid sites is too small for
generating the sample.
Flags
- -a
- Also draw sites from outside the current region's limits. this option does not
make much sense, if you also specify a raster mask with raster=[name].
- -q
- Quiet operation: do not display progress on screen.
Parameters
- input=name
- Sites map to draw sample from.
- output=name
- Sites map to store random sample in.
- size=value
- Size of the sample to generate in percent of input sites.
- raster=name
- Specify a raster to act as a mask: only sites that fall into non-NULL cells of this
raster have a chance to end up in the random sample.
- cachesize=value
- On systems with lots of memory, setting cachesize to the number of rows in the current region
can speed up operations, because the input raster map can be kept in memory.
The default of '-1' lets the program figure out a good size for the cache itself.
This option is only useful if you also specify a raster mask with raster=[name].
Notes
This program was originally developed as part of the GRASS 5 DST Predictive Modelling Toolkit
AUTHOR
Benjamin Ducke,
University of Kiel, Germany
Last changed: 2005/21/07