On 16-02-16 05:04, Thomas Adams wrote:
Giuseppe,
Unless I have misunderstood, in GRASS use r.mapcalc...
First set you region for your area of interest, for example:
g.region -dp e=2614612.5 w=1423987.5 n=-4624387.5 s=-5862637.5
Then:
r.mapcalc expression="outputMap=25.4"
where 25.4 is your value of interest, and finally:
r.out.gdal input=outputMap output=outputFileName format=GTiff
Best,
Tom
On Mon, Feb 15, 2016 at 9:33 PM, Giuseppe Amatulli
<giuseppe.amatu...@gmail.com <mailto:giuseppe.amatu...@gmail.com>> wrote:
Hi,
I would like to create an uniform random raster, similar to what i
would obtain in R with the following code
raster=raster(matrix(runif(54210, max=50, min=-50, 139,390) ,
...........)
writeRaster(raster,filename=random.tif",formats=GTiff,overwrite=TRUE)
I read the explanation of
https://grass.osgeo.org/grass7/manuals/r.random.surface.html
and also r.mapcalc - random (a,b)
but I'm not sure if one of them produce the same concept/result.
That function creates random surface(s) with spatial dependence (there
is a small typo in the link, it should be grass70). What you want, I
think, is the r.surf.random function
(https://grass.osgeo.org/grass70/manuals/r.surf.random.html). The
r.mapcalc - random(a,b) should also do what you want, it also gives a
uniform distribution.
p.s. some of the brackets in your R code above are off, it should
probably be something like raster=raster(matrix(runif(54210, max=50,
min=-50), 139,390) , ...........). Like Thomas wrote, in GRASS you first
need to define your region and set your resolution (check out g.region
for all settings, including the option to set number of rows and
columns). Than you can run r.surf.random or r.mapcalc to generate your
new random surface layer.
Any input? or better explanation
Thanks
Best
Giuseppe
--
Giuseppe Amatulli, Ph.D.
Department of Ecology and Evolutionary Biology, Yale University.
Jetz Lab, OML Room 405
P.O. Box 208106
165 PROSPECT ST
New Haven, CT 06520-8106
Teaching: spatial-ecology.net <http://spatial-ecology.net>
Work: http://sbsc.yale.edu/giuseppe-amatulli
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--
Thomas E Adams, III
2330 Jack Warner PKWY, #334
Tuscaloosa, AL 35401
1 (513) 739-9512 (cell)
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