R help - Nov 2011 - Creating a list from all combinations of two lists

R-helpers:

Say I have two lists of arbitrary elements, e.g.:

 list1=list(c(1:3),"R is fun!",c(3:6))

list2=list(c(10:5),c(5:3),c(13,5),"I am so confused")


I would like to produce a single new list that is composed of all
combinations of the "top level" of list1 and list2, e.g.:

listcombo=list(list(list1[[1]],list2[[1]]),list(list1[[1]],list2[[2]]
),...,list(list1[[length(list1)]],list2[[length(list2]]))

What is the most efficient way to do this?  Thanks!

--j

-- 
Jonathan A. Greenberg, PhD
Assistant Professor
Department of Geography
University of Illinois at Urbana-Champaign
607 South Mathews Avenue, MC 150
Urbana, IL 61801
Phone: 415-763-5476
AIM: jgrn307, MSN: jgrn307@hotmail.com, Gchat: jgrn307, Skype: jgrn3007
http://www.geog.illinois.edu/people/JonathanGreenberg.html

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On 11/22/2011 06:31 AM, Jonathan Greenberg wrote:
> R-helpers:
>
> Say I have two lists of arbitrary elements, e.g.:
>
>   list1=list(c(1:3),"R is fun!",c(3:6))
>
> list2=list(c(10:5),c(5:3),c(13,5),"I am so confused")
>
>
> I would like to produce a single new list that is composed of all
> combinations of the "top level" of list1 and list2, e.g.:
>
> listcombo=list(list(list1[[1]],list2[[1]]),list(list1[[1]],list2[[2]]
> ),...,list(list1[[length(list1)]],list2[[length(list2]]))
>
> What is the most efficient way to do this?  Thanks!
>
Hi Jonathan,
The makeIntersectList function (plotrix) does this for the attribute 
labels that represent the top level sets. However, it assumes that the 
attribute labels are character variables. You may be able to generalize 
the code to handle arbitrary objects.

Jim