[R] Accessing selected elements of a list

[Rui Barradas]

Hello,

Just try

jlist[ sapply(jlist,length) > 0 ]

Hope this helps,

Rui Barradas
Em 08-11-2012 14:42, Gonçalo Ferraz escreveu:
> Hi,
>
>
> If I have a vector:
>
> junk <- c(2,0,0,3,0)
>
> and want to access, say, all the elements that are greater than zero. I just do:
>
> junk[which(junk>0)]
>
>
>
> Now, If I have a list:
>
> jlist <- list(NULL,c(1,0),NULL,c(1,2,3), NULL)
>
> and want to access all the elements that have length greater than zero, I know how to find the elements with:
>
> which(sapply(jlist,length)>0)
>
> But how do I get a new list, only with the non-zero-length elements, without having to write a for loop?
>
> I tried:
>
> notnull <- which(sapply(jlist,length)>0)
> jlist[[notnull]]
>
> and got the error:
>
> Error in jlist[[notnull]] : recursive indexing failed at level 2
>
> Thank you for any help!
>
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