R help - May 2010 - Selecting first 7 elements

Hi,

I have a list of 100, each list has 20 elements, and I would like to
select the first 7 elements in each list.
Let's take the alphabet as an example.

x <- lapply(1:100, function(i) sample(LETTERS))

I tried x[[1:7]], but it doesn't work. Can anyone enlighten me on how
to do such selections?

Thank you.

Kang Min

Kang Min wrote:
> Hi,
> 
> I have a list of 100, each list has 20 elements, and I would like to
> select the first 7 elements in each list.
> Let's take the alphabet as an example.
> 
> x <- lapply(1:100, function(i) sample(LETTERS))
> 
> I tried x[[1:7]], but it doesn't work. Can anyone enlighten me on how
> to do such selections?
"[" is a function, and you want to use it on each element of the list,
so...

lapply(x, "[", c(1:7))

> "[" is a function, and you want to use it on each element of the
list,
> so...
> 
> lapply(x, "[", c(1:7))
and the call to c() is of course not necessary, since ":" will
generate a vector.

Thanks a lot, it works!

On May 23, 3:10?pm, Erik Iverson <er... at ccbr.umn.edu>
wrote:
> > "[" is a function, and you want to use it on each element of
the list,
> > so...
>
> > lapply(x, "[", c(1:7))
>
> and the call to c() is of course not necessary, since ":" will
generate a vector.
>
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