[R] count combined occurrences of categories

[David Winsemius]

On Jan 11, 2013, at 2:54 AM, Biau David wrote:

> Dear all,
>
> i would like to count the number of times where I have combined  
> occurrences of the categories of 2 variables.
>
> For instance, in the dataframe below, i would like to know how many  
> times each author (au1, au2, au3 represent the first, second, third  
> author) is associated with each of the category of the variable  
> 'nam'. The position of the author does not matter.
>
> nam <- c('da', 'ya', 'da', 'da', 'fr', 'fr', 'fr', 'da', 'ya', 'fr')
> au1 <- c('deb', 'art', 'deb', 'seb', 'deb', 'deb', 'mar', 'mar',  
> 'joy', 'joy')
> au2 <- c('art', 'deb', 'mar', 'deb', 'joy', 'mar', 'art', 'lio',  
> 'nem', 'mar')
> au3 <- c('mar', 'lio', 'joy', 'mar', 'art', 'lio', 'nem', 'art',  
> 'deb', 'tat')
> tutu <- data.frame(cbind(nam, au1, au2, au3))

You should first abandon the practice of using `cbind` inside  
`data.frame`. Obscure errors will plague your R experience until you  
do so.

Bas solution:

 > tutus <- data.frame(nam=tutu$nam, au=with(tutu, c(au1,au2,au3)))
 > tutab <- with(tutus, table(nam, au)  )
 > tutab
     au
nam  1 2 3 4 5 6 7
   da 2 3 1 2 4 0 0
   fr 2 2 2 2 2 1 1
   ya 1 2 1 1 0 1 0

-- 

David Winsemius, MD
Alameda, CA, USA