[R] Summarizing elements of a list

[R. Michael Weylandt]

Here's a slight modification that is even faster if speed is a consideration:

sapply(Version1_, `[[`, "First")

The thought process is to go through the list "Version1_" and apply
the operation `[[` to each element individually. This requires a
second operator (here the element name "First") which we pass through
the "..." of sapply() -- I hope that helps you get a sense of the
mechanics. We use sapply() instead of lapply() because it does some
internal simplification for us to get one big vector back, effectively
cutting out the "unlist" of the first solution I gave you.

Michael

On Fri, Dec 2, 2011 at 2:04 PM, LCOG1 <jroll at lcog.org> wrote:
> Great, this worked the fastest of all the suggestions.  Cheers,
>
> Josh
>
> ________________________________
> From: Michael Weylandt [via R] [mailto:ml-node+s789695n4144941h1 at n4.nabble.com]
> Sent: Thursday, December 01, 2011 8:11 PM
> To: ROLL Josh F
> Subject: Re: Summarizing elements of a list
>
> Similarly, this might work:
>
> unlist(lapply(Version1_, `[`,"First"))
>
> Michael
>
> On Thu, Dec 1, 2011 at 9:41 PM, Sarah Goslee <[hidden email]</user/SendEmail.jtp?type=node&node=4144941&i=0>> wrote:
>
>> How about:
>>
>> lapply(Version1_, subset, subset=c(TRUE, FALSE))
>> or sapply() depending on what you want the result to look like.
>>
>> Thanks for the reproducible example.
>>
>> Sarah
>>
>> On Thu, Dec 1, 2011 at 5:17 PM, LCOG1 <[hidden email]</user/SendEmail.jtp?type=node&node=4144941&i=1>> wrote:
>>> Hi everyone,
>>>   I looked around the list for a while but couldn't find a solution to my
>>> problem.  I am storing some results to a simulation in a list and for each
>>> element i have two separate vectors(is that what they are called, correct my
>>> vocab if necessary). See below
>>>
>>> Version1_<-list()
>>> for(i in 1:5){
>>>        Version1_[[i]]<-list(First=rnorm(1),Second=rnorm(1))
>>> }
>>>
>>> What I want is to put all of the elements' 'First' vectors into a single
>>> list to box plot. But whats a more elegant solution to the below?
>>>
>>> c(Version1_[[1]]$First,Version1_[[2]]$First,Version1_[[3]]$First,Version1_[[4]]$First,Version1_[[5]]$First)
>>>
>>> since i have 50 or more simulations this is impractical and sloppy.  Do I
>>> need to store my data differently or is their a solution on the back end?
>>> Thanks all.
>>>
>>> Josh
>>>
>> --
>> Sarah Goslee
>> http://www.functionaldiversity.org
>>
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>
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