[R] Fast way to determine number of lines in a file

Henrik Bengtsson hb at stat.berkeley.edu
Mon Feb 8 16:21:34 CET 2010

I was looking for a fast line counter as well a while ago and ended up
writing a small function in R:

  countLines() in the R.utils package

At least at the time, it was faster than readLines() [for unknown
reasons].  It is also more memory efficient.  It supports connections.
 I don't think it beats a system call to 'wc', though.  When there
will be a faster solution available, it'll be calling that instead.
It does not avoid reading the file twice.


On Mon, Feb 8, 2010 at 4:17 PM, hadley wickham <h.wickham at gmail.com> wrote:
> Hi Ken,
>> How about something like
>> length(readLines(fname))
> I'm trying to avoid the overhead of reading the file in twice.  (I'm
> trying to preallocate a data structure for a chunked read)
> Hadley
> --
> http://had.co.nz/
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