[R] Transform pairwise observations into a table
David Winsemius
dwinsemius at comcast.net
Tue Oct 2 04:33:23 CEST 2012
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
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