Milton Ribeiro wrote:
> Given a moving window (maybe with r.neihbors), I need to select a random
> value which occurs within the window. Is there any function for this in
> grass?
No.
You could either modify r.neighbors, or use e.g. grass.script.array
(example script attached).
--
Glynn Clements <[email protected]>
#!/usr/bin/env python
#%Module
#% description: Select a random cell from a moving window
#% keywords: raster
#%end
#%option G_OPT_R_INPUT
#%end
#%option G_OPT_R_OUTPUT
#%end
#%option
#% key: size
#% type: integer
#% required: yes
#% multiple: no
#% description: Size of window in raster cells
#%end
import numpy as np
import grass.script as grass
from grass.script.array import array
null = -0x80000000
def main():
input = options['input']
output = options['output']
size = int(options['size'])
if size % 2 == 0:
grass.fatal(_("Window size must be odd"))
radius = (size - 1) / 2
src = array(dtype = np.int32)
src.read(input, null = null)
rows, cols = src.shape
orows = rows - size + 1
ocols = cols - size + 1
out = array(dtype = np.int32)
out[...] = null
dst = out[radius:-radius,radius:-radius]
ix = np.arange(ocols)
for row in xrange(orows):
dx,dy = np.random.randint(0, size, size=(2,ocols))
x = ix + dx
y = row + dy
dst[row,:] = src[y,x]
dst.write(output, null = null)
if __name__ == "__main__":
options, flags = grass.parser()
main()
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