How to break a string up into overlapping sets of 3

Question

If I have multiple strings like:

skhdsfiiuwkncyeuhrsl
sdskkjheocbsill
sldkjflsdkjb

How can I program the output to be the overlapping triplets, for example, I want it to output:

skh, khd, hds, ..., rsl
sds, dsk, skk, ..., ill
sld, ldk, dkj, ..., kjb

what have you tried so far? something like `sapply(1:(nchar(x)-2), function(i) substring(x, i, i+2))` maybe? — Aramis7d, Sep 13 '17 at 17:18

score 4 · Answer 1 · answered Sep 13 '17 at 17:14

substring works:

x = c("skhdsfiiuwkncyeuhrsl", "sdskkjheocbsill", "sldkjflsdkjb", "ab")
n = 3
lapply(x, function(z) 
  if ((nc <- nchar(z)) >= n) 
    substring(z, seq(1, nc - n + 1), seq(n, nc)) 
  else 
    character(0)
)

which gives

[[1]]
 [1] "skh" "khd" "hds" "dsf" "sfi" "fii" "iiu" "iuw" "uwk" "wkn" "knc" "ncy"
[13] "cye" "yeu" "euh" "uhr" "hrs" "rsl"

[[2]]
 [1] "sds" "dsk" "skk" "kkj" "kjh" "jhe" "heo" "eoc" "ocb" "cbs" "bsi" "sil"
[13] "ill"

[[3]]
 [1] "sld" "ldk" "dkj" "kjf" "jfl" "fls" "lsd" "sdk" "dkj" "kjb"

[[4]]
character(0)

cmaher · Accepted Answer · 2017-09-13T17:35:47.070

2

Taking inspiration from this answer, Here's a one-liner:

strings <- c("skhdsfiiuwkncyeuhrsl",
"sdskkjheocbsill",
"sldkjflsdkjb")

sapply(strings, function(x) substring(x, seq(1,nchar(x)-2,1), seq(3,nchar(x),1)))

# $skhdsfiiuwkncyeuhrsl
#  [1] "skh" "khd" "hds" "dsf" "sfi" "fii" "iiu" "iuw" "uwk" "wkn" "knc" "ncy" "cye" "yeu" "euh"
# [16] "uhr" "hrs" "rsl"

# $sdskkjheocbsill
#  [1] "sds" "dsk" "skk" "kkj" "kjh" "jhe" "heo" "eoc" "ocb" "cbs" "bsi" "sil" "ill"

# $sldkjflsdkjb
#  [1] "sld" "ldk" "dkj" "kjf" "jfl" "fls" "lsd" "sdk" "dkj" "kjb"

edited Sep 13 '17 at 17:35

answered Sep 13 '17 at 17:17

cmaher

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1

@Frank thanks, copied the wrong line -- I corrected those mistakes :) – cmaher Sep 13 '17 at 17:37
How can this be used to make quadruplets or 5? – Keshav M Nov 07 '17 at 16:18

score 1 · Answer 3 · answered Sep 13 '17 at 17:17

a <- "skhdsfiiuwkncyeuhrsl"
b <- "sdskkjheocbsill"
c <- "sldkjflsdkjb"

make_triplets <- 
  function(X){
    nTriplets <- length(2:(nchar(X)-1))
    triplets <- character(nTriplets)
    for(i in 2:(nchar(X)-1)){
      triplets[i-1] <- substr(X, i - 1, i + 1)
    }
    return(triplets)
  }
make_triplets(a)

make_triplets(b)

make_triplets(c)

How to break a string up into overlapping sets of 3

3 Answers3