[R] ragged array with append

[Chuck Cleland]

Alexy Khrabrov wrote:
> I wonder what's the right way in R to do the following -- placing  
> objects of the same kind together in subarrays of varying length.   
> Here's what I mean:
> 
>  > word <- c("a","b","c","d","e","f","g","h","i","j")
>  > kind <- c(1,1,1,2,3,4,5,5,7,7)
>  > d <- data.frame(word,kind)
>  > d
>     word kind
> 1     a    1
> 2     b    1
> 3     c    1
> 4     d    2
> 5     e    3
> 6     f    4
> 7     g    5
> 8     h    5
> 9     i    7
> 10    j    7
> 
> Now from this data frame, I want to assemble words of the same kind  
> into lists.  The result should look like (not R syntax):
> 
> 1 => [a,b,c]
> 2 => [d]
> 3 => [e]
> 4 => [f]
> 5 => [g,h]
> 7 => [i,j]
> 
> What is the most appropriate data structure in R for this result and  
> growing these sublists most effectively with append?

  It would make sense to use a list as the data structure, and here is
how you might do it:

with(d, split(word, kind))

# OR

with(d, split(as.character(word), kind))

?split

> Cheers,
> Alexy
> 
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Chuck Cleland, Ph.D.
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