# [R] expand gridded matrix to higher resolution

Jeff Newmiller jdnewmil at dcn.davis.ca.us
Wed Jul 5 16:57:05 CEST 2017

```You probably ought to be using the raster package. See the CRAN Spatial Task View.
--
Sent from my phone. Please excuse my brevity.

On July 5, 2017 12:20:28 AM PDT, "Anthoni, Peter (IMK)" <peter.anthoni at kit.edu> wrote:
>Hi all,
>(if me email goes out as html, than my email client don't do as told,
>
>We need to downscale climate data and therefore first need to expand
>the climate from 0.5deg to the higher resolution 10min, before we can
>add high resolution deviations. We basically need to have the original
>data at each gridcell replicated into 3x3 gridcells.
>A simple for loop can do this, but I could need a faster procedure.
>Anybody know a faster way? Is there package than can do what we need
>I tried matrix with rep, but I am missing some magic there, since it
>doesn't do what we need.
>replicate might be promising, but then still need to rearrange the
>output into the column and row format we need.
>
>A simple example:
>mm=matrix(1:15,nrow=3,byrow = T)
>xmm=matrix(NA,nrow=nrow(mm)*3,ncol=ncol(mm)*3)
>for(icol in 1:ncol(mm)) {
>  for(irow in 1:nrow(mm)) {
>    xicol=(icol-1)*3 +c(1:3)
>    xirow=(irow-1)*3 +c(1:3)
>    xmm[xirow,xicol]=mm[irow,icol]
>  }
>}
>mm
>> > mm
>>      [,1] [,2] [,3] [,4] [,5]
>> [1,]    1    2    3    4    5
>> [2,]    6    7    8    9   10
>> [3,]   11   12   13   14   15
>>
>xmm
>> > xmm
>>       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12]
>[,13] [,14] [,15]
>>  [1,]    1    1    1    2    2    2    3    3    3     4     4     4
>   5     5     5
>>  [2,]    1    1    1    2    2    2    3    3    3     4     4     4
>   5     5     5
>>  [3,]    1    1    1    2    2    2    3    3    3     4     4     4
>   5     5     5
>>  [4,]    6    6    6    7    7    7    8    8    8     9     9     9
>  10    10    10
>>  [5,]    6    6    6    7    7    7    8    8    8     9     9     9
>  10    10    10
>>  [6,]    6    6    6    7    7    7    8    8    8     9     9     9
>  10    10    10
>>  [7,]   11   11   11   12   12   12   13   13   13    14    14    14
>  15    15    15
>>  [8,]   11   11   11   12   12   12   13   13   13    14    14    14
>  15    15    15
>>  [9,]   11   11   11   12   12   12   13   13   13    14    14    14
>  15    15    15
>
>I tried various rep with matrix, but don't get the right result.
>xmm2=matrix(rep(rep(mm,each=3),times=3),nrow=nrow(mm)*3,ncol=ncol(mm)*3,byrow
>= F)
>> identical(xmm,xmm2)
>[1] FALSE
>
>rr=replicate(3,rep(t(mm),each=3))
>rr
>> > rr
>>       [,1] [,2] [,3]
>>  [1,]    1    1    1
>>  [2,]    1    1    1
>>  [3,]    1    1    1
>>  [4,]    2    2    2
>>  [5,]    2    2    2
>>  [6,]    2    2    2
>>  [7,]    3    3    3
>> ...
>identical(xmm,matrix(rr,ncol=15,nrow=9,byrow=T))
>> > identical(xmm,matrix(rr,ncol=15,nrow=9,byrow=T))
>> [1] FALSE
>
>
>cheers
>Peter
>
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