[R] complexity of operations in R
Jan van der Laan
rhelp at eoos.dds.nl
Thu Jul 19 21:36:49 CEST 2012
On 07/19/2012 06:11 PM, Bert Gunter wrote:
> Hadley et. al:
>
> Indeed. And using a loop is a poor way to do it anyway.
>
> v <- as.list(rep(FALSE,dotot))
>
> is way faster.
>
> -- Bert
I agree that not using a loop is much faster, but I assume that the
original question is about the situation where the size of the end
result is not known. The values FALSE in the vector/list are just
examples of results from a more complex computation. But indeed avoid
loops where possible (and often this is possible).
Jan
> On Thu, Jul 19, 2012 at 8:50 AM, Hadley Wickham <hadley at rice.edu> wrote:
>> On Thu, Jul 19, 2012 at 8:02 AM, Jan van der Laan <rhelp at eoos.dds.nl> wrote:
>>> Johan,
>>>
>>> Your 'list' and 'array doubling' code can be written much more efficient.
>>>
>>> The following function is faster than your g and easier to read:
>>>
>>> g2 <- function(dotot) {
>>> v <- list()
>>> for (i in seq_len(dotot)) {
>>> v[[i]] <- FALSE
>>> }
>>> }
>> Except that you don't need to pre-allocate lists...
>>
>> Hadley
>>
>> --
>> Assistant Professor / Dobelman Family Junior Chair
>> Department of Statistics / Rice University
>> http://had.co.nz/
>>
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>
>
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