[R] make sample() faster

[Rainer M. Krug]

Thanks for the info - so the solution would (likely) be to draw several 
samples and use these whenever I need a new one.

tHANKS, i'LL TRY IT OUT,

rAINER

P.S: somebody said once that the caps-lock key is the most useless key 
on the keyboard and he is right...


Prof Brian Ripley wrote:
> I think the problem is not sample (which is written in C), but that you 
> are calling it with size=1.  Taking one sample with probabilities from a 
> large discrete distribution is necessarily slow, but you can take a large 
> sample for little more cost.
> 
> On Thu, 14 Jun 2007, Rainer M. Krug wrote:
> 
>> Hi
>>
>> I have a simulation which is relatively slow. I used Rprofile() and
>> identified the calls to sample() as the culprit is sample():
>>
>>> summaryRprof("Documents/PostDoc/Aloe_Pillansii/R/create.out")
>> $by.self
>>                   self.time self.pct total.time total.pct
>> "sample"               1.30     44.2       1.52      51.7
>> "ifelse"               0.46     15.6       2.44      83.0
>> .
>> .
>> .
>>
>> I am using sample() as follow:
>> result <- sample(
>>                  x=d.growth.seedling$growth,
>>                  size=1,
>>                  prob=d.growth.seedling$p,
>>                  replace
>>                  )
>>
>> d.growth.seedling$p and d.growth.seedling$growth have a length of 1024
>> and are calculated initially by using density().
>>
>> My question: is there any way to make this faster, i.e. replace sample()
>> as I use it with another faster algorithm (if necessary implemented in C)?
>>
>> Thanks in advance,
>>
>> Rainer
>>
>>
> 


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