Try this:
tab <- crossprod(as.matrix(ratings[,-1]))
tab <- tab - diag(diag(tab))
tab
tab / nrow(ratings)
On 2/22/07, Michael Wexler <[EMAIL PROTECTED]> wrote:
> Using R version 2.4.1 (2006-12-18) on Windows, I have a dataset which
> resembles this:
>
> id att1 att2 att3
> 1 1 1 0
> 2 1 0 0
> 3 0 1 1
> 4 1 1 1
>
> ratings <- data.frame(id = c(1,2,3,4), att1 = c(1,1,0,1), att2 = c(1,0,0,1),
> att3 = c(0,1,1,1))
>
> I would like to get a cross tab of counts of co-ocurrence, which might
> resemble this:
>
> att1 att2 att3
> att1 2 1
> att2 2 2
> att3 1 2
>
> with the hope of understanding, at least pairwise, what things "hang
> together". (Yes, there are much, much better ways to do this statistically
> including clustering and binary corrected correlation, but the audience I am
> working with asked for this version for a specific reason.)
>
> (Later on, I would also like to convert to percentages of the total unique
> pop, so the final version of the table would be
>
>
> att1 att2 att3
>
> att1 50% 25%
>
> att2 50% 50%
>
> att3 25% 50%
>
>
> But I can do this in excel if I can get the first table out.)
>
> I have tried the reshape library, but could not get anything resembling this
> (both on its own, as well as feeding in to table()). (I have also played
> with transposing and using some comments from this list from 2002 and 2004,
> but the questioners appear to assume more knowledge than I have in use of R;
> the example in the posting guide was also more complex than I was ready for,
> I'm afraid.)
>
> Sample of some of my efforts:
> library(reshape)
> melt(ratings,id=c("id"))
>
> ds1 <- melt(ratings,id=c("id"))
> table(ds1$variable, ds1$variable) # returns only rowcounts, 3 along diagonal
> xtabs(formula = value ~ ds1$variable + ds1$variable , data=ds1) # returns
> only a single row of collapsed counts, appears to not allow 1 variable in
> multiple uses
>
> I suspect I am close, so any nudges in the right direction would be helpful.
>
> Thanks much, Michael
>
> PS: www.rseek.org is very impressive, I heartily encourage its use.
>
>
> [[alternative HTML version deleted]]
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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