[R] Alternating between "for loops"

[Mercier Eloi]

Or, assuming you only have 4 different elements :

mat<- matrix(rep(c(1,2,"A", "B"),each=10),10,10, byrow=F)
mat2 <- as.data.frame(mat)

mat
       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
  [1,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [2,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [3,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [4,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [5,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [6,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [7,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [8,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
  [9,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
[10,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"

mat2
    V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
1   1  2  A  B  1  2  A  B  1   2
2   1  2  A  B  1  2  A  B  1   2
3   1  2  A  B  1  2  A  B  1   2
4   1  2  A  B  1  2  A  B  1   2
5   1  2  A  B  1  2  A  B  1   2
6   1  2  A  B  1  2  A  B  1   2
7   1  2  A  B  1  2  A  B  1   2
8   1  2  A  B  1  2  A  B  1   2
9   1  2  A  B  1  2  A  B  1   2
10  1  2  A  B  1  2  A  B  1   2

Cheers,

Eloi

On 12-07-30 04:28 PM, Rui Barradas wrote:
> Hello,
>
> Maybe something along the lines of
>
> J <- 10
> cols <- rep(c(TRUE, TRUE, FALSE, FALSE), 3)[seq_len(J)]
> for(i in which(cols)) { do something }
> for(i in which(!cols)) { do something else }
>
> Hope this helps,
>
> Rui Barradas
>
> Em 31-07-2012 00:18, Claudia Penaloza escreveu:
>> Dear All,
>> I would like to apply two different "for loops" to each set of four 
>> columns
>> of a matrix (the loops here are simplifications of the actual loops I 
>> will
>> be running which involve multiple if/else statements).
>> I don't know how to "alternate" between the loops depending on which 
>> column
>> is "running through the loop" at the time.
>> ## Set up matrix
>> J <- 10
>> N <- 10
>> y <- matrix(0,N,J)
>> ## Apply this loop to the first two of every four columns ([,1:2],
>> [,5:6],[,9:10], etc.)
>> for (q in 1:N){
>> for(j in 1:J){
>> if(j %% 2){
>> y[q,j]=1
>> }else{y[q,j]=2}
>> }
>> }
>> ## Apply this loop to the next two of every four columns
>> ([,3:4],[,7:8],[,11:12], etc.)
>> for (q in 1:N){
>> for(j in 1:J){
>> if(j %% 2){
>> y[q,j]="A"
>> }else{y[q,j]="B"}
>> }
>> }
>> I want to get something like this (preferably without the quotes):
>>
>>> y
>> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
>>   [1,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [2,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [3,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [4,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [5,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [6,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [7,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [8,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>   [9,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>> [10,] "1"  "2"  "A"  "B"  "1"  "2"  "A"  "B"  "1"  "2"
>>
>>
>>
>> Any help greatly appreciated!
>>
>> Claudia
>>
>>     [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide 
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>


-- 
Eloi Mercier
Bioinformatics PhD Student, UBC
Paul Pavlidis Lab
2185 East Mall
University of British Columbia
Vancouver BC V6T1Z4