[R] Set up a while loop

From: Rodrigo Gularte <rjgularte_at_ucdavis.edu>
Date: Tue, 18 Nov 2008 09:52:08 -0800


I am attempting to sample 10 markers from each chromosome, with a maximum distance of 14, calculated by the location of the marker in each chromosome as loc[i+1] - loc[i]. I presume the easiest way to do this is with a while loop, so that the function keeps re-sampling when the max distains is greater than 14. Example code is below.

I have gone as far as to select markers and calculate the distances, A while loop with set with max(distances)>14 should work, but I'm not sure where to set this.
Any help would be appreciated.

Rodrigo

#some markers, chromosomes and locations
loc<- rep(1:100, 5)
marker<- paste("A", seq(1:500), sep="")
chr<- rep(1:5, rep(100,5))
mm<- data.frame(marker, chr, loc)

selectmarkers<-
function(n=10){
  tapply(mm$marker, mm$chr, function(m){

# while (max(distances) > 14) {

     mars<- sort(sample(m, n))

    distances<- rep(NA, (length(mars)-1))

    for (i in 1:(length(mars)-1)) {

      distances[i]<- mm[mars[i+1], 'loc'] - mm[mars[i], 'loc']
      } #end of for loop

# } # end of while loop

    return (mars)

    } # end of tapply f(m)
  ) #tapply
} # end of selectmarkers    


Rodrigo J Gularte

Juan Medrano Laboratory

Department of Animal Science

University of California, Davis

Tel: (530) 752-4509  

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