[R] Successive subsets from a vector?
I'd like to pick every imbricated five character long subsets from a
vector. I guess there is some efficient way to do this without loops...
Here is a for-loop-version and a model for output:
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6);
ADDRESSES=c();
for(i in 1:(length(VECTOR)-4)){
ADDRESSES[i]=paste(VECTOR[i:(i+4)],collapse=)
}
ADDRESSES
[1] 14265 42650 265011 6501110 5011104 0111043
1110436 104368
[9] 43686
Atte Tenkanen
University of Turku, Finland
[[alternative text/enriched version deleted]]
__
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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Re: [R] Successive subsets from a vector?
embed(VECTOR, 5)[, 5:1]
gives the subsets, so something like
apply(embed(VECTOR, 5)[, 5:1], 1, paste, collapse=)
does the job.
The following is a bit more efficient
ind - 1:(length(VECTOR)-4)
do.call(paste, c(lapply(0:4, function(j) VECTOR[ind+j]), sep=))
but by looking at how embed() works it could be made as efficient.
Larger example:
VECTOR - sample(1:10, 1e5, replace=TRUE)
system.time(apply(embed(VECTOR, 5)[, 5:1], 1, paste, collapse=))
[1] 5.73 0.05 5.81 NA NA
system.time({ind - 1:(length(VECTOR)-4)
+ do.call(paste, c(lapply(0:4, function(j) VECTOR[ind+j]), sep=))
+ })
[1] 1.00 0.01 1.01 NA NA
The loop method took 195 secs. Just assigning to an answer of the correct
length reduced this to 5 secs. e.g. use
ADDRESSES - character(length(VECTOR)-4)
Moral: don't grow vectors repeatedly.
On Tue, 22 Aug 2006, kone wrote:
I'd like to pick every imbricated five character long subsets from a
vector. I guess there is some efficient way to do this without loops...
Here is a for-loop-version and a model for output:
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6);
ADDRESSES=c();
You do not need the semicolons, and they just confuse readers.
for(i in 1:(length(VECTOR)-4)){
ADDRESSES[i]=paste(VECTOR[i:(i+4)],collapse=)
}
ADDRESSES
[1] 14265 42650 265011 6501110 5011104 0111043
1110436 104368
[9] 43686
Atte Tenkanen
University of Turku, Finland
[[alternative text/enriched version deleted]]
__
R-help@stat.math.ethz.ch 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.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UKFax: +44 1865 272595
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R-help@stat.math.ethz.ch mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Successive subsets from a vector?
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6)
x - lapply(seq(length(VECTOR)-4),function(z)paste(VECTOR[z:(z+4)],
collapse=''))
unlist(x)
[1] 14265 42650 265011 6501110 5011104 0111043 1110436
104368 43686
On 8/22/06, kone [EMAIL PROTECTED] wrote:
I'd like to pick every imbricated five character long subsets from a
vector. I guess there is some efficient way to do this without loops...
Here is a for-loop-version and a model for output:
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6);
ADDRESSES=c();
for(i in 1:(length(VECTOR)-4)){
ADDRESSES[i]=paste(VECTOR[i:(i+4)],collapse=)
}
ADDRESSES
[1] 14265 42650 265011 6501110 5011104 0111043
1110436 104368
[9] 43686
Atte Tenkanen
University of Turku, Finland
[[alternative text/enriched version deleted]]
__
R-help@stat.math.ethz.ch 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.
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
[[alternative HTML version deleted]]
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Re: [R] Successive subsets from a vector?
Thanks!
I have used tons of for- and while-loops (I'm ashamed to reveal these scripts,
but I'm primarily a musician;-)
http://users.utu.fi/attenka/SetTheoryScripts.r), taken some or more cup of
cocoa and mostly been happy ;-) Now I got so many new ways to do these things,
that it takes a while to ruminate all the ideas here.
Atte
embed(VECTOR, 5)[, 5:1]
gives the subsets, so something like
apply(embed(VECTOR, 5)[, 5:1], 1, paste, collapse=)
does the job.
The following is a bit more efficient
ind - 1:(length(VECTOR)-4)
do.call(paste, c(lapply(0:4, function(j) VECTOR[ind+j]), sep=))
but by looking at how embed() works it could be made as efficient.
Larger example:
VECTOR - sample(1:10, 1e5, replace=TRUE)
system.time(apply(embed(VECTOR, 5)[, 5:1], 1, paste, collapse=))
[1] 5.73 0.05 5.81 NA NA
system.time({ind - 1:(length(VECTOR)-4)
+ do.call(paste, c(lapply(0:4, function(j) VECTOR[ind+j]), sep=))
+ })
[1] 1.00 0.01 1.01 NA NA
The loop method took 195 secs. Just assigning to an answer of the
correct
length reduced this to 5 secs. e.g. use
ADDRESSES - character(length(VECTOR)-4)
Moral: don't grow vectors repeatedly.
On Tue, 22 Aug 2006, kone wrote:
I'd like to pick every imbricated five character long subsets
from a
vector. I guess there is some efficient way to do this without
loops... Here is a for-loop-version and a model for output:
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6);
ADDRESSES=c();
You do not need the semicolons, and they just confuse readers.
for(i in 1:(length(VECTOR)-4)){
ADDRESSES[i]=paste(VECTOR[i:(i+4)],collapse=)
}
ADDRESSES
[1] 14265 42650 265011 6501110 5011104 0111043
1110436 104368
[9] 43686
Atte Tenkanen
University of Turku, Finland
[[alternative text/enriched version deleted]]
__
R-help@stat.math.ethz.ch 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.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UKFax: +44 1865 272595
__
R-help@stat.math.ethz.ch 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.
Re: [R] Successive subsets from a vector?
The loop method took 195 secs. Just assigning to an answer of the correct length reduced this to 5 secs. e.g. use ADDRESSES - character(length(VECTOR)-4) Moral: don't grow vectors repeatedly. Other languages (eg. Java) grow the size of the vector independently of the number of observations in it (I think Java doubles the size whenever the vector is filled), thus changing O(n) behaviour to O(log n). I've always wondered why R doesn't do this. Hadley __ R-help@stat.math.ethz.ch 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.
Re: [R] Successive subsets from a vector?
On Tue, 22 Aug 2006, hadley wickham wrote: The loop method took 195 secs. Just assigning to an answer of the correct length reduced this to 5 secs. e.g. use ADDRESSES - character(length(VECTOR)-4) Moral: don't grow vectors repeatedly. Other languages (eg. Java) grow the size of the vector independently of the number of observations in it (I think Java doubles the size whenever the vector is filled), thus changing O(n) behaviour to O(log n). I've always wondered why R doesn't do this. At one point at least that was too expensive on memory/address space (and it may still be for 32-bit OSes). There is even a 'truelength' field in the vector header to allow for such a strategy, and the strategy is used in scan() and elsewhere. In my experience it is relatively rare not to know the vector length in advance in R code. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UKFax: +44 1865 272595 __ R-help@stat.math.ethz.ch 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.
Re: [R] Successive subsets from a vector?
Like this:
do.call( paste, c( list(sep=), lapply(1:5,function(x)
VECTOR[x:(length(VECTOR)-5+x)]) ))
[1] 14265 42650 265011 6501110 5011104 0111043 1110436
104368 43686
HTH,
Chuck
On Tue, 22 Aug 2006, kone wrote:
I'd like to pick every imbricated five character long subsets from a
vector. I guess there is some efficient way to do this without loops...
Here is a for-loop-version and a model for output:
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6);
ADDRESSES=c();
for(i in 1:(length(VECTOR)-4)){
ADDRESSES[i]=paste(VECTOR[i:(i+4)],collapse=)
}
ADDRESSES
[1] 14265 42650 265011 6501110 5011104 0111043
1110436 104368
[9] 43686
Atte Tenkanen
University of Turku, Finland
[[alternative text/enriched version deleted]]
[ Part 3.64: Included Message ]
Charles C. Berry(858) 534-2098
Dept of Family/Preventive Medicine
E mailto:[EMAIL PROTECTED] UC San Diego
http://biostat.ucsd.edu/~cberry/ La Jolla, San Diego 92093-0717
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Successive subsets from a vector?
Here is a solution that uses gsub with a negative lookahead perl-style
regexp to do it:
VECTOR - c(1,4,2,6,5,0,11,10,4,3,6,8,6)
e -
([[:digit:]]+),(?=([[:digit:]]+),([[:digit:]]+),([[:digit:]]+),([[:digit:]]+))
out - gsub(e, \\1\\2\\3\\4\\5 , paste(VECTOR, collapse = ,), perl = TRUE)
head(strsplit(out, )[[1]], -1) # uses head from R 2.4.0
On 8/22/06, kone [EMAIL PROTECTED] wrote:
I'd like to pick every imbricated five character long subsets from a
vector. I guess there is some efficient way to do this without loops...
Here is a for-loop-version and a model for output:
VECTOR=c(1,4,2,6,5,0,11,10,4,3,6,8,6);
ADDRESSES=c();
for(i in 1:(length(VECTOR)-4)){
ADDRESSES[i]=paste(VECTOR[i:(i+4)],collapse=)
}
ADDRESSES
[1] 14265 42650 265011 6501110 5011104 0111043
1110436 104368
[9] 43686
Atte Tenkanen
University of Turku, Finland
[[alternative text/enriched version deleted]]
__
R-help@stat.math.ethz.ch 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@stat.math.ethz.ch mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
