[R] pairs

[David Winsemius]

I stuck in another "7" in one of the lines with a 2 and reasoned that  
we could deal with the desire for non-ordered "pair counting" by  
pasting min(x,y) to max(x,y);

 > dput(prmtx)
structure(c(2, 1, 3, 9, 5, 7, 7, 8, 1, 7, 6, 5, 6, 2, 2, 7), .Dim =  
c(4L,
4L))
 > prmtx
      [,1] [,2] [,3] [,4]
[1,]    2    5    1    6
[2,]    1    7    7    2
[3,]    3    7    6    2
[4,]    9    8    5    7

 > pair.str <- sapply(1:nrow(prmtx), function(z)   
apply(combn(prmtx[z,], 2), 2,function(x) paste(min(x[2],x[1]),  
max(x[2],x[1]), sep=".")))

The logic:
sapply(1:nrow(prmtx), ... just loops over the rows of the matrix.
combn(prmtx[z,], 2)  ... returns a two row matrix of combination in a  
single row.
apply(combn(prmtx[z,], 2), 2 ... since combn( , 2)  returns a matrix  
that has two _rows_ I needed to loop over the columns.
paste(min(x[2],x[1]), max(x[2],x[1]), sep=".") ... stick the minimum  
of a pair in front of the max and separates them with a period to  
prevent two+ digits from being non-unique

Then using table() and logical tests in an index for the desired  
multiple pairs:


 > tpair <-table(pair.str)
 > tpair
pair.str
1.2 1.5 1.6 1.7 2.3 2.5 2.6 2.7 3.6 3.7 5.6 5.7 5.8 5.9 6.7 7.7 7.8  
7.9 8.9
   2   1   1   2   1   1   2   3   1   1   1   1   1   1   1   1   1    
1   1
 > tpair[tpair>1]
pair.str
1.2 1.7 2.6 2.7
   2   2   2   3

-- 
David.

On Nov 16, 2009, at 7:02 AM, David Winsemius wrote:

> I'm not convinced it's right. In fact, I'm pretty sure the last step  
> taking only the first half of the list is wrong. I also do not know  
> if you have considered how you want to count situations like:
>
> 3 2 7 4 5 7 ...
> 7 3 8 6 1 2 9 2 ......
>
> How many "pairs" of 2-7/7-2 would that represent?
>
> -- 
> David
> On Nov 15, 2009, at 11:06 PM, cindy Guo wrote:
>
>> Hi, David,
>>
>> The matrix has 20 columns.
>> Thank you very much for your help. I think it's right, but it seems  
>> I need some time to figure it out. I am a green hand. There are so  
>> many functions here I never used before. :)
>>
>> Cindy
>>
>> On Sun, Nov 15, 2009 at 5:19 PM, David Winsemius <dwinsemius at comcast.net 
>> > wrote:
>> Assuming that the number of columns is 4, then consider this  
>> approach:
>>
>> > prs <-scan()
>> 1: 2 5 1 6
>> 5: 1 7 8 2
>> 9: 3 7 6 2
>> 13: 9 8 5 7
>> 17:
>> Read 16 items
>> prmtx <- matrix(prs, 4,4, byrow=T)
>>
>> #Now make copus of x.y and y.x
>>
>> pair.str <- sapply(1:nrow(prmtx), function(z)  
>> c(apply(combn(prmtx[z,], 2), 2,function(x) paste(x[1],x[2],  
>> sep=".")) , apply(combn(prmtx[z,], 2), 2,function(x)  
>> paste(x[2],x[1], sep="."))) )
>> tpair <-table(pair.str)
>>
>> # This then gives you a duplicated list
>> > tpair[tpair>1]
>> pair.str
>> 1.2 2.1 2.6 2.7 6.2 7.2 7.8 8.7
>> 2   2   2   2   2   2   2   2
>>
>> # So only take the first half of the pairs:
>> > head(tpair[tpair>1], sum(tpair>1)/2)
>>
>> pair.str
>> 1.2 2.1 2.6 2.7
>> 2   2   2   2
>>
>> -- 
>> David.
>>
>>
>>
>> On Nov 15, 2009, at 8:06 PM, David Winsemius wrote:
>>
>> I could of course be wrong but have you yet specified the number of  
>> columns for this pairing exercise?
>>
>> On Nov 15, 2009, at 5:26 PM, cindy Guo wrote:
>>
>> Hi, All,
>>
>> I have an n by m matrix with each entry between 1 and 15000. I want  
>> to know
>> the frequency of each pair in 1:15000 that occur together in rows.  
>> So for
>> example, if the matrix is
>> 2 5 1 6
>> 1 7 8 2
>> 3 7 6 2
>> 9 8 5 7
>> Pair (2,6) (un-ordered) occurs together in rows 1 and 3. I want to  
>> return
>> the value 2 for this pair as well as that for all pairs. Is there a  
>> fast way
>> to do this avoiding loops? Loops take too long.
>>
>> and provide commented, minimal, self-contained, reproducible code.
>>                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>
>> David Winsemius, MD
>> Heritage Laboratories
>> West Hartford, CT
>>
>> ______________________________________________
>> 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
>> and provide commented, minimal, self-contained, reproducible code.
>>
>> David Winsemius, MD
>> Heritage Laboratories
>> West Hartford, CT
>>
>>
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
> ______________________________________________
> 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
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT