On Tue, Feb 17, 2015 at 5:30 PM, Markus Neteler <nete...@osgeo.org> wrote:
> On Tue, Feb 17, 2015 at 4:49 PM, Margherita Di Leo <direg...@gmail.com> > wrote: > > Hi, > > > > I have a vector of points. According to a regular grid, I need to > (randomly) > > sample a certain number n of these points in each cell of the grid. Such > > number n is given in a column of the attribute table of the grid. How > would > > you do this? > > With a small script this should be doable: > - generate the grid as polygons (v.mkgrid) > - loop over each polygon > - fetch category number or v.extract > - fetch corresponding number of points to be created from DB > - v.random, using the current grid polygon for restricted creation > feature > > http://grass.osgeo.org/grass70/manuals/v.random.html#restriction-to-vector-areas Here lies the problem. I need to randomly pick points that are already existing. Example: for grid cell that has ID 42, I have 50 points, and have to randomly pick 7 out of these 50. > > - save point map > - patch all point maps into single resulting map > - remove single point maps > > Something like this... > > Markus > -- Best regards, Dr. Margherita DI LEO Scientific / technical project officer European Commission - DG JRC Institute for Environment and Sustainability (IES) Via Fermi, 2749 I-21027 Ispra (VA) - Italy - TP 261 Tel. +39 0332 78 3600 margherita.di-...@jrc.ec.europa.eu Disclaimer: The views expressed are purely those of the writer and may not in any circumstance be regarded as stating an official position of the European Commission.
_______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user