[R-sig-Geo] Fastest method to reclassify large raster.

[Lionel Hertzog]

Dear Nevil Amos,

Maybe the function 'reclassify' in the raster package is what you are 
looking for.

Yours,
Lionel

On 13/09/2013 08:36, nevil amos wrote:
> I have a large raster (4gb as a .asc file) with 197000 values, that I need
> to reclassify by values in  an large lookup table, 197,000rowsx80reclass
> value columns.
>
> I have tried using sub in a loop to replace the values, however the process
> is taking hours, without even completing the first of the
>   reclassifications.
>
> I would be grateful for any suggestions of processes that I can use to
> speed the reclass process ( I need files that can be read back into ARCGIS
> at the end of the process.
>
> My current script is
>
> library(raster)
> r<-raster("Raster.asc")
>
> COLS<-names(mydataOut[,5:88])
>
> for (i in COLS){
>
>    subs(r,mydataOut,by="Value",which=i,filename=paste(i,".asc",sep=""))
>    print(paste ("done", i))
> }
>
>
> Many thanks
>
> Nevil Amos
>
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>
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