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Identifying sequences

6 messages · David Winsemius, ONKELINX, Thierry, Jonathan Daily +2 more

Original
David Winsemius
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On Jun 1, 2011, at 6:27 AM, christiaan pauw wrote:

            

      
      
      
    

        
You probably want something like

 > which(diff(x) >1)
[1] 10 21

Or perhaps what the rle function provides.

?diff
?rle

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      ONKELINX, Thierry
    

    

      
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Something like this?

a=1:10
b=20:30
c=40:50
x=c(a,b,c)
borders <- which(diff(x) != 1)
seqs <- data.frame(start = c(1, borders + 1), end = c(borders, length(x)))

Best regards,

Thierry

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Jonathan Daily
    

    

      
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I am assuming in this case that you are looking for continuity along
integers, so if you expect noninteger values this will not work.

You can get the index of where breaks can be found in your example using

which(diff(x) > 1)

        
On Wed, Jun 1, 2011 at 6:27 AM, christiaan pauw <cjpauw at gmail.com> wrote:

            

      
      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      christiaan pauw
    

    

      
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Thanks to David, Thierry and Jonathan for your help.
I have been able to put this function together

a=1:10
b=20:30
c=40:50
x=c(a,b,c)

seq.matrix <- function(x){
lower<- x[which(diff(x) != 1)]
upper <- x[which(diff(x) != 1)+1]
extremities <- c(1,lower, upper,x[length(x)])
m <- data.frame(matrix(extremities[order(extremities)],ncol=2,byrow=TRUE,dimnames=list(rows=paste("group",1:(length(lower)+1),sep=""),cols=c("lower","upper"))))
m$length=m$upper-m$lower+1
m
}

s.m=seq.matrix(x)
s.m
       lower upper length
group1     1    10     10
group2    20    30     11
group3    40    50     11

One can then make a test to see if a certain value (say 9) falls
within one of the groups and use that to find the group name or lower
or upper border

s.m.test=function(s.m,i){which(s.m[,1] <i & i < s.m[,2])}
s.m.test(s.m,i=9)
[1] 1
e.g.
row.names(s.m)[s.m.test(s.m,i=9)]
[1] "group1"

Cheers
Christiaan

        
On 1 June 2011 14:31, Jonathan Daily <biomathjdaily at gmail.com> wrote:

            

      
      
      
    

        

      
      
    

            

      
      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Mike Marchywka
    

    

      
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As I understand, you are looking for large derivatives
or approx discontinuity against smooth signal.
This seems like a natural application for wavelets,
try the haar wavelet and use package 
wavelets,

            

      
      
      
    

        
$W1
      [,1]
 [1,]   49
 [2,]   -1
 [3,]   -1
 [4,]   -1
 [5,]   -1
 [6,]   -1
 [7,]   -1
 [8,]   -1
 [9,]   -1
[10,]   -1
[11,]  -10
[12,]   -1
[13,]   -1
[14,]   -1
[15,]   -1
[16,]   -1
[17,]   -1
[18,]   -1
[19,]   -1
[20,]   -1
[21,]   -1
[22,]  -10
[23,]   -1
[24,]   -1
[25,]   -1
[26,]   -1
[27,]   -1
[28,]   -1
[29,]   -1
[30,]   -1
[31,]   -1
[32,]   -1