Hi,
what is the most effective way to assign randomly
the values -1,0 and 1 to a raster map, where each of
the three values should occur in one third of the map.
Furthermore I’d like to assign to 10 % of the cell
the values -1 and 10% the value 1 and to the remaining
80% the value 0 (or any other arbitrary combination of
the three values). Is there any fast way in G7 or do I need
to play with r.random, r.mask and r.mapcalc and r.patch.
Maybe someone has already had such a task…
so any suggestion is welcome.
cheers,
Johannes
Johannes Radinger <johannesradinger@gmail.com> writes:
Hi,
what is the most effective way to assign randomly
the values -1,0 and 1 to a raster map, where each of
the three values should occur in one third of the map.
Furthermore I'd like to assign to 10 % of the cell
the values -1 and 10% the value 1 and to the remaining
80% the value 0 (or any other arbitrary combination of
EXACTLY 10%, or with a probability of 10?
If EXACTLY, I guess you have to use different functions (select 10%
random cells, assign -1, mask them out, select again 10% of the ORIGINAL
NUMBER of cells, assigh=n 1, assgn 0 to the rest)
Otherwise, you can use the random() function in r.mapcalc:
r < 0.1 -> assign 1
r > 0.9 -> assign -1
otherwise assign 0
Hope this helps,
Rainer
the three values). Is there any fast way in G7 or do I need
to play with r.random, r.mask and r.mapcalc and r.patch.
Maybe someone has already had such a task...
so any suggestion is welcome.
cheers,
Johannes
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Rainer M. Krug
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