[R-sig-Geo] Best raster of raster stack

[Jonathan Greenberg]

Small mod: the above works with version 1.3.4 or later of
spatial.tools (on R-forge, at the time of this email) -- if you are
using an earlier version (e.g. the one on CRAN at the time of this
email), you need to slightly modify the function headers to include
ellipses:

max_of_rasters <- function(raster1,raster2,...)

max_of_stack <- function(stack1,...)


On Sat, Mar 8, 2014 at 2:33 PM, Jonathan Greenberg <jgrn at illinois.edu> wrote:
> Just to throw yet another solution into the pot, here's how to do this
> with rasterEngine (which will allow for parallel processing of your
> input to potentially speed your process up):
>
> # Individual rasters as inputs approach:
> library(spatial.tools)
> raster1 <- raster(system.file("external/tahoe_lidar_bareearth.tif",
> package="spatial.tools"))
> raster2 <- raster(system.file("external/tahoe_lidar_highesthit.tif",
> package="spatial.tools"))
>
> sfQuickInit() # Spawns a number of parallel workers = half your CPUs
> (you can mod this with the cpus= parameter)
> max_of_rasters <- function(raster1,raster2)
> {
> output <- pmax(raster1,raster2)
> dim(output) <- c(dim(raster1)[1:2],1)
> return(output)
> }
>
> max_of_rasters_output <-
> rasterEngine(raster1=raster1,raster2=raster2,fun=max_of_rasters,debugmode=FALSE)
>
> # Combining all the rasters into a single stack approach (probably
> easier for your application):
> max_of_stack <- function(stack1)
> {
> output <- apply(stack1,1:2,max)
> dim(output) <- c(dim(stack1)[1:2],1)
> return(output)
> }
>
> stack1 <- stack(raster1,raster2)
> max_of_stack_output <-
> rasterEngine(stack1=stack1,fun=max_of_stack,debugmode=FALSE)
>
> sfQuickStop() # Turn off the parallel processing engine.
>
> On Sat, Mar 8, 2014 at 10:15 AM, Maurizio Marchi
> <mauriziomarchi85 at gmail.com> wrote:
>> Tanks a lot for your suggestions. maybe there will be a lot of different
>> ways to do that but merging your scripts I found exactly what I wanted to
>> do:
>>
>> # beginning
>> library(raster)
>> r1 <- raster(matrix(c(1,1,1,2,2,2,4,4,4), ncol = 3))
>> r2 <- raster(matrix(c(2,2,2,3,3,3,1,1,1), ncol = 3))
>> r3 <- raster(matrix(c(5,5,5,1,1,1,2,2,2), ncol = 3))
>> r <- stack(r1,r2,r3)
>> plot(r)
>> #?calc
>> res1<-calc(r,fun=max) # single raster map with maximum values of all 3
>> rasters
>> plot(res1)
>> # end
>>
>>  Now let's see if my i5 processor is able to process 22 raster maps
>> with 77,760,000
>> cells each.... :)
>>
>> thank You very much again!!
>>
>> --
>> Maurizio Marchi, PhD student
>> CRA-SEL (Arezzo, Italy)
>> www.selvicoltura.eu
>> ID skype: maurizioxyz
>> *Ubuntu 12.04 LTS*
>> *"Il bello dell'open-source è che le domande possono essere poste alla
>> fonte"*
>> *utente linux 552.742*
>>
>>         [[alternative HTML version deleted]]
>>
>>
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>>
>
>
>
> --
> Jonathan A. Greenberg, PhD
> Assistant Professor
> Global Environmental Analysis and Remote Sensing (GEARS) Laboratory
> Department of Geography and Geographic Information Science
> University of Illinois at Urbana-Champaign
> 259 Computing Applications Building, MC-150
> 605 East Springfield Avenue
> Champaign, IL  61820-6371
> Phone: 217-300-1924
> http://www.geog.illinois.edu/~jgrn/
> AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307, Skype: jgrn3007



-- 
Jonathan A. Greenberg, PhD
Assistant Professor
Global Environmental Analysis and Remote Sensing (GEARS) Laboratory
Department of Geography and Geographic Information Science
University of Illinois at Urbana-Champaign
259 Computing Applications Building, MC-150
605 East Springfield Avenue
Champaign, IL  61820-6371
Phone: 217-300-1924
http://www.geog.illinois.edu/~jgrn/
AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307, Skype: jgrn3007