[R] extracting vectors from lists of lists

[Phil Spector]

Jennifer -
    Does this do what you want?

> v1 = sapply(output,'[[','vec')
> v2 = sapply(output,'[[','other')
> v1
      [,1] [,2]
[1,]    1    6
[2,]    2    7
[3,]    3    8
[4,]    4    9
[5,]    5   10
> v2
[1] "stuff" "stuff"

(in more readable form:

v1 = sapply(output,function(x)x$vec)
v2 = sapply(output,function(x)x$other)    )


Notice that if the objects returned by sapply are not conformable,
it will return its result in a list.


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Fri, 11 Dec 2009, Jennifer Young wrote:

> Good evening
>
> I often have as output from simulations a list of various values, vectors
> and matrices.
> Supposing that I then run said simulation several times, I often want to
> extract a particular result from each simulation for plotting and,
> ideally, put it in a matrix.
>
> A simple example
>
> v1 <- 1:5
> v2 <- 6:10
> other1 <- "stuff"
> other2 <- "stuff"
>
> set1 <- list(v1,other1)
> names(set1) <- c("vec","other")
> set2 <- list(v2,other2)
> names(set2) <- c("vec","other")
>
> output <- list(set1, set2)
>
>
> Is there some form of lapply() that will allow me to extract v1 and v2
> (ie, the $vec elements) from both sets?
> Bonus if I can then put it into a matrix tidily.
>
> many thanks
> Jennifer Young
>
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