[R] random sample from arrays

[Joris Meys]

Could you elaborate?

Both

 x <- 1:40000
 set <- matrix(nrow = 50, ncol = 11)
  for(i in c(1:11)){
    set[,i] <-sample(x,50)
    print(c(i,"->", set), quote = FALSE)
   }

and

 x <- 1:40000
 set <- matrix(nrow = 50, ncol = 11)
 for(i in c(1:50)){
   set[i,] <-sample(x,11)
   print(c(i,"->", set), quote = FALSE)
  }

run perfectly fine on my computer.
Cheers


On Fri, Jul 9, 2010 at 3:10 PM, Assa Yeroslaviz <frymor at gmail.com> wrote:
> Hi Joris,
> I guess i did it wrong again.
> but your example didn't work either. I still get the error massage.
>
> but replicate function just fine. I can even replicate the whole array
> lines.
>
> THX
>
> Assa
>
> On Thu, Jul 8, 2010 at 15:20, Joris Meys <jorismeys at gmail.com> wrote:
>>
>> Don't know what exactly you're trying to do, but you make a matrix
>> with 11 columns and 50 rows, then treat it as a vector. On top of
>> that, you try to fill 50 rows/columns with 50 values. Off course that
>> doesn't work. Did you check the warning messages when running the
>> code?
>>
>> Either do :
>>
>>  for(i in c(1:11)){
>>    set[,i] <-sample(x,50)
>>    print(c(i,"->", set), quote = FALSE)
>>   }
>>
>> or
>>
>>  for(i in c(1:50)){
>>    set[i,] <-sample(x,11)
>>    print(c(i,"->", set), quote = FALSE)
>>   }
>>
>> Or just forget about the loop altogether and do :
>>
>> set <- replicate(11,sample(x,50))
>> or
>> set <- t(replicate(50,sample(x,11)))
>>
>> cheers
>>
>> On Thu, Jul 8, 2010 at 8:04 AM, Assa Yeroslaviz <frymor at gmail.com> wrote:
>> > Hello R users,
>> >
>> > I'm trying to extract random samples from a big array I have.
>> >
>> > I have a data frame of over 40k lines and would like to produce around
>> > 50
>> > random sample of around 200 lines each from this array.
>> >
>> > this is the matrix
>> >          ID xxx_1c xxx__2c xxx__3c xxx__4c xxx__5T xxx__6T xxx__7T
>> > xxx__8T
>> > yyy_1c yyy_1c _2c
>> > 1 A_512  2.150295  2.681759  2.177138  2.142790  2.115344  2.013047
>> > 2.115634  2.189372  1.643328  1.563523
>> > 2 A_134 12.832488 12.596373 12.882581 12.987091 11.956149 11.994779
>> > 11.650336 11.995504 13.024494 12.776322
>> > 3 A_152  2.063276  2.160961  2.067549  2.059732  2.656416  2.075775
>> > 2.033982  2.111937  1.606340  1.548940
>> > 4 A_163  9.570761 10.448615  9.432859  9.732615 10.354234 10.993279
>> > 9.160038  9.104121 10.079177  9.828757
>> > 5 A_184  3.574271  4.680859  4.517047  4.047096  3.623668  3.021356
>> > 3.559434  3.156093  4.308437  4.045098
>> > 6 A_199  7.593952  7.454087  7.513013  7.449552  7.345718  7.367068
>> > 7.410085  7.022582  7.668616  7.953706
>> > ...
>> >
>> > I tried to do it with a for loop:
>> >
>> > genelist <- read.delim("/user/R/raw_data.txt")
>> > rownames(genelist) <- genelist[,1]
>> > genes <- rownames(genelist)
>> >
>> > x <- 1:40000
>> > set <- matrix(nrow = 50, ncol = 11)
>> >
>> > for(i in c(1:50)){
>> >    set[i] <-sample(x,50)
>> >    print(c(i,"->", set), quote = FALSE)
>> >    }
>> >
>> > which basically do the trick, but I just can't save the results outside
>> > the
>> > loop.
>> > After having the random sets of lines it wasn't a problem to extract the
>> > line from the arrays using subset.
>> >
>> > genSet1 <-sample(x,50)
>> > random1 <- genes %in% genSet1
>> > subsetGenelist <- subset(genelist, random1)
>> >
>> >
>> > is there a different way of creating these random vectors or saving the
>> > loop
>> > results outside tjhe loop so I cn work with them?
>> >
>> > Thanks a lot
>> >
>> > Assa
>> >
>> >        [[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.
>> >
>>
>>
>>
>> --
>> Joris Meys
>> Statistical consultant
>>
>> Ghent University
>> Faculty of Bioscience Engineering
>> Department of Applied mathematics, biometrics and process control
>>
>> tel : +32 9 264 59 87
>> Joris.Meys at Ugent.be
>> -------------------------------
>> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
>
>



-- 
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Applied mathematics, biometrics and process control

tel : +32 9 264 59 87
Joris.Meys at Ugent.be
-------------------------------
Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php