[R] writing sample values in to a file

[Dieter Menne]

chandu wrote:
> 
>   I am relatively new to R. I would like to know how can we write the
> realizations (for example generated through rnorm or runif) in to a data
> file. It would be very inefficient to first generate values and then write
> them in to file using "write" function. Instead, is there a way to
> generate 1 value at a time and append them in to the file.
> 

"It would be very inefficient". Sounds like you tried it.

n = 30000
system.time(for (i in 1:n){
    cat(rnorm(1),file="a.txt",append=TRUE)
 }
)
system.time(write.table(rnorm(n),file="b.txt"))
 )
  
 user  system elapsed 
   3.98    8.66   16.11 

> system.time(write.table(rnorm(n),file="b.txt"))
   user  system elapsed 
   0.59    0.01    0.61 

So the inefficient method is about 25 times faster.

Dieter



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