r - Paste the elements of two columns -

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this question has answer here:

i have data.frame of following kind

set.seed(12) d = data.frame(a=sample(5,x=1:9),                 b=sample(5,x=1:9),                c=sample(5,x=1:9),                d=sample(5,x=1:9),                e=sample(5,x=1:9),                f=sample(5,x=1:9))  d #   b c d e f # 1 1 1 4 4 2 3 # 2 7 2 7 9 7 5 # 3 8 5 3 8 1 2 # 4 2 9 8 7 5 9 # 5 9 6 2 1 9 4

i take first 2 columns, convert integer characters , paste 2 elements of same row together. repeat process each successive pair of columns.

here script job correctly:

bar = function (twocols) {sapply(1:nrow(twocols), fun=function(x) {paste(twocols[x,], collapse="")} )}      count = 0     out = matrix(0, ncol=ncol(d)/2, nrow=nrow(d))     (i in seq(1,ncol(d), 2)) {        count = count+1        out[,count] = bar(d[,i:(i+1)])     }  print(out)      [,1] [,2] [,3] [1,] "11" "44" "23" [2,] "72" "79" "75" [3,] "85" "38" "12" [4,] "29" "87" "59" [5,] "96" "21" "94"

but data.frame big , looping through whole data.frame in r slow. have more efficient solution? rcpp might solution don't know how code in c++.

this matches description, not output show:

mat = as.matrix(d)  matrix(paste0(mat[, seq(1, ncol(mat), = 2)],               mat[, seq(2, ncol(mat), = 2)]),        ncol = ncol(mat) / 2)  #      [,1] [,2] [,3] # [1,] "11" "44" "23" # [2,] "72" "79" "75" # [3,] "85" "38" "12" # [4,] "29" "87" "59" # [5,] "96" "21" "94"

you could, of course, convert result numeric, data.frame, etc.


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