R help - Jun 2009 - Extracting Sequence Data from a Vector

Thanks in advance.
I have a vector of numbers which contain sections that are sequences 
which increase by a value of 1 followed by a gap in the data and then 
another sequence occurs, etc:

x<-c(1:3, 6: 7, 10:13)

 From the vector I need to extract 2 items of information A) the first 
number in the sequence (e.g., 1, 6, 10) and B) how many observations 
were in each  sequence section (e.g., 3, 2, 4).

v1   v2
1      3
6      2
10    4

It seems simple, but my R skills are still in their infancy so I very 
much appreciate the help.
Eric

-- 
Eric Vander Wal
Ph.D. Candidate
University of Saskatchewan, Department of Biology,
112 Science Place, Saskatoon, SK., S7N 5E2

"Pluralitas non est ponenda sine neccesitate"

try this:
> x
[1]  1  2  3  6  7 10 11 12 13
> # find breaks
> breaks <- c(FALSE, diff(x) != 1)
> # now create matrix with groupings (just for visual)
> z <- data.frame(x, cumsum(breaks))
> # create list with first element of each seq and the length
> t(sapply(split(z, z[,2]), function(b) c(b[1,1], nrow(b))))
  [,1] [,2]
0    1    3
1    6    2
2   10    4


On Wed, Jun 10, 2009 at 1:28 PM, Eric Vander Wal
<eric.vanderwal@usask.ca>wrote:
> Thanks in advance.
> I have a vector of numbers which contain sections that are sequences which
> increase by a value of 1 followed by a gap in the data and then another
> sequence occurs, etc:
>
> x<-c(1:3, 6: 7, 10:13)
>
> From the vector I need to extract 2 items of information A) the first
> number in the sequence (e.g., 1, 6, 10) and B) how many observations were
in
> each  sequence section (e.g., 3, 2, 4).
>
> v1   v2
> 1      3
> 6      2
> 10    4
>
> It seems simple, but my R skills are still in their infancy so I very much
> appreciate the help.
> Eric
>
> --
> Eric Vander Wal
> Ph.D. Candidate
> University of Saskatchewan, Department of Biology,
> 112 Science Place, Saskatoon, SK., S7N 5E2
>
> "Pluralitas non est ponenda sine neccesitate"
>
> ______________________________________________
> 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<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 that you are trying to solve?

	[[alternative HTML version deleted]]

jim holtman wrote:
> try this:
>
>   
Oh well, i spent the time writing this so i might as well post my 
(almost identical) solution,

x<-c(1:3, 6: 7, 10:13)

breaks = c(TRUE, diff(x) != 1)

data.frame(start = x[breaks], length = tabulate(cumsum(breaks)))

Hoping this works,

baptiste

>> x
>>     
> [1]  1  2  3  6  7 10 11 12 13
>   
>> # find breaks
>> breaks <- c(FALSE, diff(x) != 1)
>> # now create matrix with groupings (just for visual)
>> z <- data.frame(x, cumsum(breaks))
>> # create list with first element of each seq and the length
>> t(sapply(split(z, z[,2]), function(b) c(b[1,1], nrow(b))))
>>     
>   [,1] [,2]
> 0    1    3
> 1    6    2
> 2   10    4
>
>
> On Wed, Jun 10, 2009 at 1:28 PM, Eric Vander Wal <eric.vanderwal at
usask.ca>wrote:
>
>   
>> Thanks in advance.
>> I have a vector of numbers which contain sections that are sequences
which
>> increase by a value of 1 followed by a gap in the data and then another
>> sequence occurs, etc:
>>
>> x<-c(1:3, 6: 7, 10:13)
>>
>> From the vector I need to extract 2 items of information A) the first
>> number in the sequence (e.g., 1, 6, 10) and B) how many observations
were in
>> each  sequence section (e.g., 3, 2, 4).
>>
>> v1   v2
>> 1      3
>> 6      2
>> 10    4
>>
>> It seems simple, but my R skills are still in their infancy so I very
much
>> appreciate the help.
>> Eric
>>
>> --
>> Eric Vander Wal
>> Ph.D. Candidate
>> University of Saskatchewan, Department of Biology,
>> 112 Science Place, Saskatoon, SK., S7N 5E2
>>
>> "Pluralitas non est ponenda sine neccesitate"
>>
>> ______________________________________________
>> R-help at 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<http://www.r-project.org/posting-guide.html>
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>     
>
>
>
>

On Jun 10, 2009, at 1:28 PM, Eric Vander Wal wrote:
> Thanks in advance.
> I have a vector of numbers which contain sections that are sequences  
> which increase by a value of 1 followed by a gap in the data and  
> then another sequence occurs, etc:
>
> x<-c(1:3, 6: 7, 10:13)
>
> From the vector I need to extract 2 items of information A) the  
> first number in the sequence (e.g., 1, 6, 10) and B) how many  
> observations were in each  sequence section (e.g., 3, 2, 4).
>
> v1   v2
> 1      3
> 6      2
> 10    4
>
> It seems simple, but my R skills are still in their infancy so I  
> very much appreciate the help.
> Eric
>
Yet another solution:

 > x[which(c(-Inf, diff(x)) != 1)]
[1]  1  6 10

 > diff(c(which(c(-Inf, diff(x)) != 1), length(x)+1) )
[1] 3 2 4


-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT