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       v.kcv  - Randomly partition points into test/train sets.


       vector, statistics


       v.kcv help
       v.kcv    [-dq]    input=name    output=name   k=integer   column=string
       [--overwrite]  [--verbose]  [--quiet]

           Use drand48()


           Allow output files to overwrite existing files

           Verbose module output

           Quiet module output

           Name of input vector map

           Name for output vector map

           Number of partitions
           Options: 1-32767

           Name for new column to which partition number is written
           Default: part


       v.kcv  randomly  divides  a  points  lists  into  k sets of  test/train
       data  (for  k-fold  cross validation).  Test  partitions  are  mutually
       exclusive.  That  is,  a point will appear in only one  test  partition
       and  k-1 training  partitions.  The  program  generates  a random point
       using the selected random number generator and then finds  the  closest
       point  to  it.   This  site is removed from the candidate list (meaning
       that it will not be selected for any other test  set)   and  saved   in
       the  first  test  partition file.  This is repeated until enough points
       have been selected for the test partition.   The   number   of   points
       chosen  for  test partitions depends upon the number of sites available
       and the  number of partitions chosen (this number is made as consistent
       as possible while ensuring that all sites will be chosen  for testing).
       This  process of filling up a test partition is done k times.


       An ideal random sites generator will follow a Poisson dis  only  be  as
       random  as the  original  points.   This  program simply divides points
       up in a random manner.

       Be  warned  that  random number generation occurs  over  the  intervals
       defined by the region of the map.

       This program may not work properly with Lat-long data.


       v.random and g.region


       James Darrell McCauley ,
       when he was at: Agricultural Engineering Purdue University

       Update to 5.7 Radim Blazek 10 / 2004

       Last changed: $Date: 2011-11-08 01:42:51 -0800 (Tue, 08 Nov 2011) $

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       © 2003-2013 GRASS Development Team

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