Speed trick: unlist(…, use.names=FALSE) is heaps faster!

[This article was first published on jottR, 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.

Sometimes a minor change to your R code can make a big difference in processing time. Here is an example showing that if you’re don’t care about the names attribute when unlist():ing a list, specifying argument use.names=FALSE can speed up the processing lots!

> x <- split(sample(1000, size=1e6, rep=TRUE), rep(1:1e5, times=10))
> t1 <- system.time(y1 <- unlist(x))
> t2 <- system.time(y2 <- unlist(x, use.names=FALSE))
> stopifnot(identical(y2, unname(y1)))
> t1/t2
user system elapsed
103 NaN 104

That’s more than a 100 times speedup.

So, check your code to see to which unlist() statements you can add an use.names=FALSE.

To leave a comment for the author, please follow the link and comment on their blog: jottR.

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.

Never miss an update!
Subscribe to R-bloggers to receive
e-mails with the latest R posts.
(You will not see this message again.)

Click here to close (This popup will not appear again)