Random Sampling of Plain Text in R

July 11, 2016
By

[This article was first published on #untitled, 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.

If you are mining with a text source, performing some language modelling, you need to sample from a text corpus. I was wondering how to have a function to randomly selects chunks of a text file efficiently and is doing the job fast. I wanted to keep the function as simple as possible and using basic S3 methods in R.

Solution

I heavily encourage you to use scan function that is a S3 basic R function:

sampleText <- function (filename, total, sampleSize) {  
  lineNumber = sample(total, sampleSize)
  sample <- list()
  for (line in lineNumber) {
    result <- scan(filename, what="character", skip= line, 
         nlines=1, sep="\n", strip.white = TRUE, fileEncoding = 'UTF-8')
    sample <- list(sample, result)
  }
  return(unlist(sample))
}

And here’s how to use it:

sample <- createPartition('path_to_file.txt', 2000, 10)  

Inspecting result:

> class(sample)
[1] "character"
> sample
 [1] "It's a cloudy day"                                                                                                                                                
 [2] "But I did want her to have at least PART of my imaginary Paris experience, so I used her pretty Paris stamp to make her birthday card."                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
 ...
[10] "Our smartest friend (Zachary)- was nice enough to study the injection and give us some information to share with everyone..." 

NOTE: The reason that this function is fast is that you send in a file connection. If you are working with different encoding, to change values accordingly. Also, make sure that in case you want sentences back, set sep='.'.

Hope you find this function useful! ?

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

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.



If you got this far, why not subscribe for updates from the site? Choose your flavor: e-mail, twitter, RSS, or facebook...

Comments are closed.

Search R-bloggers

Sponsors

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)