[R] how to bind lists recursively

[Gabor Grothendieck]

Unfortunately Reduce is just as slow as the slowest of
the solutions below:

Reduce(c, 0:10000, list())


On Tue, May 27, 2008 at 11:18 PM,  <Bill.Venables at csiro.au> wrote:
> This is somewhat subtle.
>
> Rolf's solution (here corrected to...)
>
> a <- list()
> for(i in 0:10000) a[[i+1]] <- i
>
> is the best of the loop solutions (or at least the best I know of).  The
> apparently similar
>
> a <- list(0)
> for(i in 1:10000) a <- c(a, list(i))
>
> will take a lot longer, although the result is the same.  For example:
>
>> system.time({
>    a <- list()
>    for(i in 0:10000) a[[i+1]] <- i
>    })
>   user  system elapsed
>   0.59    0.00    0.59
>> system.time({
>    a <- list(0)
>    for(i in 1:10000) a <- c(a, list(i))
>    })
>   user  system elapsed
>   6.87    0.00    6.89
>>
>
> That's a factor of about 11 times as long.  The best of the lot is
>
> a <- as.list(0:10000)
>
> of course, but this has problems with generalisation, (which everyone
> suspects is going to be needed here...).
>
> Bill Venables.
>
>
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Rolf Turner
> Sent: Wednesday, 28 May 2008 1:02 PM
> To: Daniel Yang
> Cc: r-help at r-project.org
> Subject: Re: [R] how to bind lists recursively
>
>
> On 28/05/2008, at 2:43 PM, Daniel Yang wrote:
>
>> Dear all,
>>
>> I want to create a list that contains 0,1,2,3, ..., 10000 as its
>> elements. I used the following code, which apparently doesn't work
>> very well.
>>
>> a <- 0
>> for(i in 1:10000) {
>>    a <- list(a, i)
>> }
>>
>> The result is not what I wanted. So how to create the bind lists
>> recursively so that the last element would be the newly added one
>> while the previous elements all remain the same?
>
> a <- list()
> for(i in 1:10000) a[[i]] <- i
>
> (The word ``bind'' is inappropriate.)
>
>        cheers,
>
>                Rolf Turner
>
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