v.random: add random sampling from vector points map

[neteler]

In v.random, there is no possibility to do random sampling from a vector points map (as r.random does). I have seen that most vector code is already in

 raster/r.random/random.c

incl DBMS support since r.random also support vector points (but only from *raster* maps). Maybe not a big issue for someone familiar with vector/DBMS...

Markus

[neteler]

The idea to use separately v.random and v.what.vect fails as it introduces new data points:

v.info -c lidar1map
g.region vect=lidar1map
v.random output=random_samples10 n=3800 --o
v.db.addtable map=random_samples10 columns='cat integer, height double precision'
v.what.vect vector=random_samples10 column=height qvector=lidar1map qcolumn=N3 dmax=100

while it should subset existing data points.

Suggestion: maybe better use v.extract and add a "random=" parameter there which populates internally the "list=" list of categories?

Markus

[neteler]

Maris wrote:

v.extract now supports extraction of N random categories matching vector features. To extract N points, simply provide random=N option. Current implementation has one small(?) problem - it operates on CAT's and not feature ID's and thus will extract ALL features matching randomly selected CAT values.

He implemented it in r33639. Tested and works fine.

Thanks, Maris,

Markus