[R] rnorm

[Ben Bolker]

Steve Lianoglou-6 wrote:
> 
> Hi,
> 
> On Jul 16, 2009, at 4:54 PM, Jose Narillos de Santos wrote:
> 
>> Hi I want to simulate random numbers normal distributed with this size
>> (2000,10000).
>>
>> I tried this but my computer exhaust there is a fast way to make it?
>>
>>
>> randz<-matrix(rnorm(2000000),2000,10000)
> 
> 
> I'll refrain from asking if you really need/want to do that, so I'll  
> just suggest that as a start you could look at the "bigmemory" package  
> for an alternative way to deal with massive matrices:
> 
> http://cran.r-project.org/web/packages/bigmemory/index.html
> 
> -steve
> 
> --
> Steve Lianoglou
> Graduate Student: Physiology, Biophysics and Systems Biology
> Weill Medical College of Cornell University
> 
> Contact Info: http://cbio.mskcc.org/~lianos/contact
> 
> 

Hmmm.  I was going to ask "why do you want to do that?", but then I tried it
and was
surprised that it wasn't particularly difficult ...

system.time(m <- matrix(rnorm(2e7),ncol=1000))
  user  system elapsed 
  5.628   0.376   6.029 

 this is on a not *terribly* fast computer (1.2 GHz processor) -- are your
results much slower?  Do you want to do this many many times (in which case
I'd ask again "why?")

[In fact, what you actually did was even faster

system.time(randz<-matrix(rnorm(2000000),2000,10000))
   user  system elapsed 
  0.732   0.164   0.894 

I'm curious whether you really intended to pick 2e6 values and put them
into a matrix with space for 2e7 values ...]


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