[R-sig-Geo] How to write functions with mutiple large raster data file (MOD13Q1, 2000-2012)

[Robert J. Hijmans]

Francisco,

I think what you want to do can be accomplished with 'calc' (as was
pointed out in another thread).

library(raster)
in <- stack(list.files(pattern=*..tif$))
out <- calc(in, fun=function(x) lowess(x,f=7/n,iter=10)$y)


But to answer your question, I think you could do:

in <- stack(list.files(pattern=*..tif$))
# and, here is the trick
out <- brick(in, values=FALSE)

Also, in your loop you could do:

getValues(in, ...
writeValues(out, ....


Best, Robert

On Tue, May 7, 2013 at 7:35 AM, Francisco Zambrano <frzambra at gmail.com> wrote:
> Hi everybody,
>
> I'm working with MODIS data MOD13Q1 and the NDVI index between 2000- today.
> I have been trying to do a function, but I have a problem when stack the
> 310 files and then I tried to use the writeStart function. I had an error
> because the startFuction work with rasterLayer or RasterBrick. But, when I
> tried to make the brick with the rasterStack (>brick(rasterStack)) the
> operation took too much time (11 hours)
>
> My question, is what is the most efficiently way to make a rasterBrick from
> multiple raster (geoTIFF) files?
>
> save the rasterStack and then open it with brick?
>
> My code is something like:
>
>>out<-stack(list.files(pattern=*..tif$))
>>out<-brick(mod) #too much time (11 hours appox)
>
>   >out<-writeStart(out,filename,overwrite=TRUE)
>   >bs<-blockSize(out)
>   >pb<-pbCreate(bs$n)
>   >for (i in 1:bs$n){
>     v<-getValues(out,row=bs$row[i],nrows=bs$nrows[i])
>     s<-t(sapply(apply(v,1,lowess,f=7/n,iter=10),"[[","y"))
>     out<-writeValues(out,s,bs$row[i])
>    pbStep(pb,i)
>   }
>
> Kind Regards
>
> Francisco Zambrano Bigiarini
>
> from Chile, latin america
>
>         [[alternative HTML version deleted]]
>
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