[R] Reading large files quickly

Gabor Grothendieck ggrothendieck at gmail.com
Sun May 10 00:10:36 CEST 2009

You could try it with sqldf and see if that is any faster.
It use RSQLite/sqlite to read the data into a database without
going through R and from there it reads all or a portion as
specified into R.  It requires two lines of code of the form:

f < file("myfile.dat")
DF <- sqldf("select * from f", dbname = tempfile())

with appropriate modification to specify the format of your file and
possibly to indicate a portion only.  See example 6 on the sqldf
home page: http://sqldf.googlecode.com
and ?sqldf

On Sat, May 9, 2009 at 12:25 PM, Rob Steele
<freenx.10.robsteele at xoxy.net> wrote:
> I'm finding that readLines() and read.fwf() take nearly two hours to
> work through a 3.5 GB file, even when reading in large (100 MB) chunks.
>  The unix command wc by contrast processes the same file in three
> minutes.  Is there a faster way to read files in R?
> Thanks!
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