[R] How to express a tree?

[Duncan Temple Lang]

Jim Lemon wrote:
> On 10/28/2009 04:06 AM, Hesen Peng wrote:
>> Hello everybody,
>>
>> I'm write a function whose output represents a tree. Can anyone please
>> recommend me some data structure in R which are good for expressing a
>> tree? The possible idea I'm having in my mind is to represent the
>> whole tree as a list in which a sublist (an element to the main list)
>> contains all its corresponding branches. Is there any simpler way of
>> doing this? Thank you very much.
>>    
> Hi Hesen,
> This is the approach used in the listBuilder function in the crank
> package. It may be of use to you.

Lists of lists is very natural. It is "hard" to find
the parent and ancestors give a particular sub-tree,
i.e. walk up the tree, should that be an issue.

The XML package also provides various implementations of trees
in R (as well as in C) using

   list of lists
   environments
   parallel vectors of
          nodes, parent indices, child indices.

It might be worth a look to see alternatives.

 D.

> 
> Jim
> 
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