[R] Optimized File Reading with R

Liaw, Andy andy_liaw at merck.com
Tue May 15 18:45:07 CEST 2007

If it's a matrix, use scan().  If the columns are not all the same type,
use the colClasses argument to read.table() to specify their types,
instead of leaving it to R to guess.  That will speed things up quite a


From: Lorenzo Isella
> Dear All,
> Hope I am not bumping into a FAQ, but so far my online search 
> has been fruitless
> I need to read some data file using R. I am using the (I think)
> standard command:
> data_150<-read.table("y_complete06000", header=FALSE)
> where y_complete06000 is a 6000 by 40 table of numbers.
> I am puzzled at the fact that R is taking several minutes to 
> read this file.
> First I thought it may have been due to its shape, but even
> re-expressing and saving the matrix as a 1D array does not help.
> It is not a small file, but not even huge (it amounts to about 5Mb of
> text file).
> Is there anything I can do to speed up the file reading?
> Many thanks
> Lorenzo
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