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question R regarding consecutive numbers

6 messages · Samir Benzerfa, Duncan Murdoch, William Dunlap +1 more

Duncan Murdoch
#
On 27/10/2011 8:43 AM, Samir Benzerfa wrote:
How about this?

 > runs <- rle(x)
 > with(runs, table(values, lengths))
       lengths
values 1 2 3
      1 2 1 1
      2 1 0 0
      3 1 0 0
      4 2 0 0
      5 2 0 0
      6 1 0 0
      9 2 0 0

Duncan
David Winsemius
#
On Oct 27, 2011, at 9:21 AM, Duncan Murdoch wrote:

            

      
      
      
    

        
And to go even a bit further, the table function returns a matrix  
which can be addressed to yield the specific answer requested:

  with(runs, table(values, lengths))["1",2]
[1] 1  # m=number of exactly runs if length 2
 > sum( tbl["1", 2:ncol(tbl)] )
[1] 2  # number of runs of length two or more.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Samir Benzerfa
    

    

      
      #
    

  


  

      
In the general case, there is still a gap in your solution >sum( tbl["1",
2:ncol(tbl)] ). This solution refers to a specific column number (here:
column number 2) and not to the actual length of the run, doesn't it? That
is, in this simple example the column number 2 actually corresponds to the
length "2", but this must not be the case in general. For instance if there
is no run of length "2" but only of length "1" and "3", the column number 2
will refer to length "3" (try it with the new vector below). I realized this
problem when applying your solution to a much more extended vector. So, the
problem is that I would have to check manually whether the column number
really corresponds to the length of runs. A possible solution would be to
force R to show all the lengths from 1:ncol even if there is no run of some
lengths in-between and just fill the whole column with zero's.

            

      
      
      
    

        
Any ideas how to solve this problem?

Cheers, S.B.


-----Urspr?ngliche Nachricht-----
Von: David Winsemius [mailto:dwinsemius at comcast.net] 
Gesendet: Donnerstag, 27. Oktober 2011 16:44
An: Duncan Murdoch
Cc: Samir Benzerfa; r-help at r-project.org
Betreff: Re: [R] question R regarding consecutive numbers

        
On Oct 27, 2011, at 9:21 AM, Duncan Murdoch wrote:

        

            

      
      
      
    

        
And to go even a bit further, the table function returns a matrix  
which can be addressed to yield the specific answer requested:

  with(runs, table(values, lengths))["1",2]
[1] 1  # m=number of exactly runs if length 2
 > sum( tbl["1", 2:ncol(tbl)] )
[1] 2  # number of runs of length two or more.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      William Dunlap
    

    

      
      #
    

  


  

      
Are you looking for something like the following?  ifactor()
is like factor but assumes that x is integral and that levels
should be {1, 2, ..., max(x)} with no gaps.

            

      
      
      
    

        
1 2 3
  1 3 0 1
  2 1 0 0
  3 1 0 0
  4 2 0 0
  5 2 0 0
  6 1 0 0
  7 0 0 0
  8 0 0 0
  9 2 0 0

Also note that tbl["2","3"] does not mean the same as tbl[2,3],
although if you use the ifactor function as above they will refer
to the same element.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

            

      
      
      
    

        

      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      David Winsemius
    

    

      
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On Oct 28, 2011, at 11:26 AM, William Dunlap wrote:

        

            

      
      
      
    

        
I answered earlier in a posting that did not get threaded properly in  
my mailer and this is  a pr?cis:

 > xtbl <- with(rle(x), table(values, lengths))
 > xtbl["1", which( as.numeric( attr(xtbl, "dimnames")$lengths) >=2 )]
3 5
1 1

Since character-numeric comparisons appear to get properly coerced the  
as numeric may not be necessary:

 > xtbl["1", which( attr(xtbl, "dimnames")$lengths >=2 )]
3 5
1 1