[R] Chopping a vector up into smaller vectors

[Stephen Eglen]

Anyone got a neat way to chop a vector up into smaller subvectors?
This is what I have now, which seems inelegant:

chop - function(v, counts) {
  stopifnot(sum(counts)==length(v))
  end - cumsum(counts)
  beg - c(1, 1+end[-length(end)])
  begend - cbind(beg, end)
  apply(begend, 1, function(x) v[x[1]:x[2]])
}
  

 chop(9:1, c(3,2,4))
[[1]]
[1] 9 8 7

[[2]]
[1] 6 5

[[3]]
[1] 4 3 2 1

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Re: [R] Chopping a vector up into smaller vectors

[Eik Vettorazzi]

Hi Stephen,
how about this:

chop-function(x,counts){
 stopifnot(sum(counts)==length(x))
 split(9:1,unlist(mapply(rep,seq_along(counts),counts)))
}
chop(9:1,c(3,2,4))

cheers

Am 02.08.2012 12:29, schrieb Stephen Eglen:
 Anyone got a neat way to chop a vector up into smaller subvectors?
 This is what I have now, which seems inelegant:
 
 chop - function(v, counts) {
   stopifnot(sum(counts)==length(v))
   end - cumsum(counts)
   beg - c(1, 1+end[-length(end)])
   begend - cbind(beg, end)
   apply(begend, 1, function(x) v[x[1]:x[2]])
 }
   
 
 chop(9:1, c(3,2,4))
 [[1]]
 [1] 9 8 7
 
 [[2]]
 [1] 6 5
 
 [[3]]
 [1] 4 3 2 1
 
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 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.
 


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Eik Vettorazzi

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University Medical Center Hamburg-Eppendorf

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Re: [R] Chopping a vector up into smaller vectors

[Petr PIKAL]

Hi

one of possible options

f- function(x, parts) split(x,rep(1:length(parts),parts))
f(9:1, c(3,2,4))
$`1`
[1] 9 8 7

$`2`
[1] 6 5

$`3`
[1] 4 3 2 1

You can also check if your parts vector agrees with x vector, if you want.

Regards
Petr


 
 Anyone got a neat way to chop a vector up into smaller subvectors?
 This is what I have now, which seems inelegant:
 
 chop - function(v, counts) {
   stopifnot(sum(counts)==length(v))
   end - cumsum(counts)
   beg - c(1, 1+end[-length(end)])
   begend - cbind(beg, end)
   apply(begend, 1, function(x) v[x[1]:x[2]])
 }
 
 
  chop(9:1, c(3,2,4))
 [[1]]
 [1] 9 8 7
 
 [[2]]
 [1] 6 5
 
 [[3]]
 [1] 4 3 2 1
 
 __
 R-help@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@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.