R devel - Oct 2010 - list comprehension to create an arbitrary-sized list with arbitrary names/values

In python, one can do this

mydict = dict([(keyfun(x), valfun(x)) for x in mylist])

to create a dictionary with whatever keys and values we want from an
input list of arbitrary size. In R, I want to similarly create a list
with names/values that are generated by some keyfun and valfun
(assuming that keyfun is guaranteed to return something suitable as a
name). How can I do this?

Hi,

On 13.10.2010, at 21:26, Steve Kim wrote:
> mydict = dict([(keyfun(x), valfun(x)) for x in mylist])
> 
> to create a dictionary with whatever keys and values we want from an
> input list of arbitrary size. In R, I want to similarly create a list
> with names/values that are generated by some keyfun and valfun
> (assuming that keyfun is guaranteed to return something suitable as a
> name). How can I do this?
Try something like this:

  mydict <- lapply(mylist, valfun)
  names(mydict) <- sapply(mylist, keyfun)

or

  mydict <- structure(lapply(mylist, valfun), names=sapply(mylist, keyfun))

Cheers
Olaf

This question probably belongs on R-help instead of R-devel.

What works best for you will depend on how big 'mylist' is.

An article discussing some possibilities can be found at:
http://opendatagroup.com/2009/07/26/hash-package-for-r/

Hope this helps,
--Erik

Steve Kim wrote:
> In python, one can do this
> 
> mydict = dict([(keyfun(x), valfun(x)) for x in mylist])
> 
> to create a dictionary with whatever keys and values we want from an
> input list of arbitrary size. In R, I want to similarly create a list
> with names/values that are generated by some keyfun and valfun
> (assuming that keyfun is guaranteed to return something suitable as a
> name). How can I do this?
> 
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