[R] Transform pairwise observations into a table

[David Winsemius]

On Oct 1, 2012, at 2:30 PM, arun wrote:

> HI AHJ,
> No problem.
> 
> One more way in addition to reshape() (Rui's suggestion) to get the same result.
> library(reshape)
> 
> as.matrix(cast(melt(dat1,id=c("ind1","ind2")),ind1~ind2,value="value"))
> #      1     2     3   4
> #1 1.000 0.250 0.125 0.5
> #2 0.250 1.000 0.125 0.5
> #3 0.125 0.125 1.000 0.5
> #4 0.500 0.500 0.500 1.0
> A.K.
> 
That looks a tad ... well, ... complicated. So perhaps these base-only solutions with tapply might be more accessible: Some of them do border on the whimsical, I will admit:

with (dat1, tapply(coef, list(ind1,ind2), I))

with (dat1, tapply(coef, list(ind1,ind2), c))

with (dat1, tapply(coef, list(ind1,ind2), "^", 1))

with (dat1, tapply(coef, list(ind1,ind2), "+", 0))

It is a specific response to the request for a `table`-like function tha twouldallow the application of other functions. Cnage the `1` to `2` in the third instance and you get the tabulated squares. And do not forget the availability of `ftable` to flatten the output of `tapply` retunred values.


-- 
David.
> 
> 
> ----- Original Message -----
> From: "Hadjixenofontos, Athena" <AHadjixenofontos at med.miami.edu>
> To: arun <smartpink111 at yahoo.com>
> Cc: R help <r-help at r-project.org>
> Sent: Monday, October 1, 2012 12:59 PM
> Subject: Re: [R] Transform pairwise observations into a table
> 
> Thank you. I had looked at xtabs but misunderstood the syntax. This is great. :)
> 
> AHJ
> 
> 
> 
> On Oct 1, 2012, at 12:53 PM, "arun" <smartpink111 at yahoo.com> wrote:
> 
>> Hi,
>> Try this:
>> 
>> dat1<-read.table(text=" 
>> ind1 ind2 coef 
>> 1 1 1 
>> 1 2 0.25 
>> 1 3 0.125 
>> 1 4 0.5 
>> 2 2 1 
>> 2 1 0.25 
>> 2 3 0.125 
>> 2 4 0.5 
>> 3 3 1 
>> 3 1 0.125 
>> 3 2 0.125 
>> 3 4 0.5 
>> 4 4 1 
>> 4 1 0.5 
>> 4 2 0.5 
>> 4 3 0.5 
>> ",sep="",header=TRUE) 
>> mat1<-as.matrix(xtabs(coef~ind1+ind2,data=dat1)) 
>> 
>> #    ind2 
>> #ind1     1     2     3     4 
>>    # 1 1.000 0.250 0.125 0.500 
>>     #2 0.250 1.000 0.125 0.500 
>>     #3 0.125 0.125 1.000 0.500 
>>     #4 0.500 0.500 0.500 1.000 
>> 
>> A.K.
>> 
>> 
>> 
>> ----- Original Message -----
>> From: AHJ <ahadjixenofontos at med.miami.edu>
>> To: r-help at r-project.org
>> Cc: 
>> Sent: Monday, October 1, 2012 12:17 PM
>> Subject: [R] Transform pairwise observations into a table
>> 
>> Hi,
>> 
>> I have a table of pairs of individuals and a coefficient that belongs to the
>> pair:
>> 
>> ind1    ind2    coef
>> 1    1    1
>> 1    2    0.25
>> 1    3    0.125
>> 1    4    0.5
>> 2    2    1
>> 2    1    0.25
>> 2    3    0.125
>> 2    4    0.5
>> 3    3    1
>> 3    1    0.125
>> 3    2    0.125
>> 3    4    0.5
>> 4    4    1
>> 4    1    0.5
>> 4    2    0.5
>> 4    3    0.5
>> 
>> And I want to convert it to a matrix where each individual is both a row and
>> a column and at the intersection of each pair is the coefficient that
>> belongs to that pair:
>> 
>>      1           2           3             4
>> 1    1           0.25           0.125    0.5
>> 2    0.25      1           0.125    0.5
>> 3    0.125    0.125    1            0.5
>> 4    0.5           0.5           0.5            1
>> 
>> If table() would allow me to specify something other than frequencies to
>> fill the table with, it would be what I need. I tried a few different
>> combinations of t() and unique() but none of it made enough sense to post as
>> my starting code... I am just lost. Any help would be greatly appreciated.
>> 
>> Thank you,
>> AHJ
>> 
>> 
>> 
>> --
>> View this message in context: http://r.789695.n4.nabble.com/Transform-pairwise-observations-into-a-table-tp4644706.html
>> Sent from the R help mailing list archive at Nabble.com.
>> 
>> ______________________________________________
>> 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.
>> 
> 
> 
> ______________________________________________
> 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
Alameda, CA, USA