[R] Too slow to execute!

[Chuck Cleland]

Usman Shehu wrote:
> Greetings,
> I have the following simple function but what worries me is that it takes about  5 or more minutes to execute. My machine runs on windows with 1.8GHz and 256 Ram.
>> Re=NULL
>> for(i in 1:100000){
> + x=rnorm(20)
> + Re[i]=(x-2*10)/20
> + Re
> + }
> I would appreciate any help on how to make it faster.

  Why use a loop here at all?  It seems like this would do it pretty fast:

Re <- rnorm(n = 2e+06, mean = - 1)

> system.time(Re <- rnorm(n = 2e+06, mean = - 1))
[1] 0.77 0.01 0.78   NA   NA

  I'm not sure what you expect Re to be (a list with 100000 vectors of
length 20?), but you could reshape one long vector into a matrix or
whatever you might need.  For example:

Re.mat <- matrix(Re, ncol=20)

> Usman
> 
> 
> 
> 
>       ___________________________________________________________
> 
> now.
> 
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> 
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Chuck Cleland, Ph.D.
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