[R] question R regarding consecutive numbers

[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.

> x=c(1,3,4,9,1,9,1,5,4,5,2,1,1,1,6)

Any ideas how to solve this problem?

Cheers, S.B.


-----Ursprüngliche 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:

> On 27/10/2011 8:43 AM, Samir Benzerfa wrote:
>> Hi  everyone
>>
>>
>>
>> Do you know about any possibility in R to check for consecutive  
>> numbers in
>> vectors? That is, I do not only want to count the number of  
>> observations in
>> total (which can be done table(x)), but I also want to count for  
>> instance
>> how many times that vector contains a certain number consecutively.
>>
>>
>>
>> For example in the following vector x the number "1" appears 7 times.
>> However, I want to check for instance how many times two  
>> consecutive 1's
>> appear in the vector, which would actually be two times the case in  
>> the
>> below vector.
>>
>>
>>
>> >  x=c(1,1,3,4,9,1,9,1,5,4,5,2,1,1,1,6)
>>
>>
>>
>> Any ideas for this issue?
>
> How about this?
>
> > runs <- rle(x)
> > with(runs, table(values, lengths))

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.


-- 
David

>

>     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
>
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David Winsemius, MD
West Hartford, CT