On Thu, Apr 3, 2014 at 5:15 PM, Matteo Mura <[email protected]> wrote: > Dear all, > > I am going to quickly explain you what I am trying to achieve. > > I have a grid of 4693 hexagons (see > https://www.dropbox.com/s/rkim7v21i1p0bet/grid.jpeg). Each hexagon has > its univocal id (ID_ES). > > We are planning a 2-phase sampling procedure. In the first phase we > identified some feature inside each hexagon (namely trees out of > forest features). Now we should carry out the second phase with ground > survey. Obviously we cannot visit each hexagon but just a sample of > them. > > In doing so we need to divide the hexagon grid in strata composed by > compact (i.e. not too much elongated in vertical or horizontal > direction) groups of adjacent hexagons, of course without replacement, > inside of each strata an hexagon will be randomly choosen and visited.
... FWIW, as of today (kudos to Markus Metz) you can also contrain v.random to single polygons: http://grass.osgeo.org/grass70/manuals/v.random.html#examples In your case you could generate a sufficiently low number of random points over your hexagon area, then intersect the resulting points with the hexagons to select them for your analysis. Something like this :) markusN _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
