[R] Write to multiple connections or multiple text files

[jim holtman]

The solution you have seems to read in all the lines of data at once,
operate on them and then write them out as a whole chunck.  Having
multiple connections open won't really help since I/O is serial.  So
is the code you included the actual code, or just an example?  It
would help to see what the real code is to see if there is some way of
optimizing it.

On Fri, Jan 23, 2009 at 8:06 AM, Andersson, Jafet
<Jafet.Andersson at eawag.ch> wrote:
> Hi all,
>
> I want to modify a large number of text files (ca 4000) by replacing a
> value found on a particular line in them with a value from an R object.
>
> For a single file I would normally use:
>        con<-file ("foo.txt", open="r+")
>        content<-readLines(con)
>        content[n]<-"test"
>        writeLines(content,con)
>        close(con)
>
> For repeating this for several files I can write a for loop around this.
> However, my problem with this is that it is rather slow. I am therefore
> wondering if there is any other way to write to multiple connections in
> a similar way as one can e.g. write to a large number of rows in a
> matrix simultaneously?
>
> (Note that seek() is not so practical for me since the number of bytes
> before the specific line varies between the files, therefore I use
> reanLines() and match the right line instead.)
>
> My Systems:
> OS: Windows Server 2003 & Linux Red Hat (interchangeably)
> R version: 2.7.2
>
> Thanks for any suggestions!
>
> ooo
> Jafet Andersson
> Eawag - The Swiss Federal Institute of Aquatic Science and Technology
> Ueberlandstrasse 133
> P.O. Box 611
> CH-8600 Duebendorf
> Switzerland
> Phone: +41 (0)44 823 5358
> Fax:     +41 (0)44 823 5028
> http://www.eawag.ch/index_EN
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?