[R] A question on Programming

[R. Michael Weylandt]

Dr Murdoch,

You're absolutely correct -- my apologies.

Michael

On Thu, Nov 10, 2011 at 10:44 AM, Duncan Murdoch
<murdoch.duncan at gmail.com> wrote:
> On 10/11/2011 10:28 AM, R. Michael Weylandt wrote:
>>
>> Yes, there will be some reduction in speed:
>>
>> E.g.,
>>
>> >  system.time(replicate(1e5, (function() sum(1:10))()))
>>    user  system elapsed
>>   0.696   0.022   0.729
>> >  system.time(replicate(1e5, sum(1:10)))
>>    user  system elapsed
>>   0.292   0.006   0.306
>>
>> But it's not much: 3 tenths of a second for 10,000 calls. It's
>> certainly worth it for ease of readibility and debugging.
>
> I don't think your test is valid:  you're not just calling the function in
> the upper loop, you're creating it too.  Here's what I see:
>
> First, the version I complained about:
>
>> system.time(replicate(1e5, (function() sum(1:10))()))
>   user  system elapsed
>   0.35    0.00    0.35
>
> Now a more realistic one:
>
>> f <- function() sum(1:10)
>> system.time(replicate(1e5, f()))
>   user  system elapsed
>   0.25    0.00    0.25
>
> Now the version with no function call:
>
>> system.time(replicate(1e5, sum(1:10)))
>   user  system elapsed
>   0.23    0.00    0.24
>
>
> So creating a function is expensive, but calling one isn't so bad.
>
> Duncan Murdoch
>