[This article was first published on Statisfaction » R, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
This short post is to share an R tip Pierre recently gave me. When you need to store values sequentially (typically inside a loop), it’s more far efficient to create the whole vector (or matrix) and to fill it, rather than to concatenate the values to your current vector (or matrix). In terms of allocation time, it’s up to 60 times faster
n=10^5
a=NULL
system.time(for (i in 1:n){a=c(a,1)})
>utilisateur système écoulé
> 12.09 0.00 12.09
b=rep(0,n)
system.time(for (i in 1:n){b[i]=1})
>utilisateur système écoulé
> 0.21 0.00 0.20
which makes a big difference. In a Gibbs sampling loop, where a lot of other computations are done, I still have gain of 25%! For other recommendations (don’t use parentheses where you can avoid them), you can have a look on this post.
To leave a comment for the author, please follow the link and comment on their blog: Statisfaction » R.
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.