[R] Partially reading a file (particularly)

[Tobin, Jared]

This is perfect, thanks for the help.

The read-in time for one of these files alone (of 30+) on this machine
improves from about 2:30 to 0:10 when using this method.

--

jared tobin, student research assistant
dept. of fisheries and oceans
tobinjr at dfo-mpo.gc.ca

-----Original Message-----
From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com] 
Sent: Thursday, May 31, 2007 10:46 AM
To: Tobin, Jared
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] Partially reading a file (particularly)

Try this:

con <- pipe("findstr /b 5 myfile.dat")
open(con, "r")
DF <- read.fwf(con, widths = c(1, 1, 2)) # replace with right args
close(con)

On 5/31/07, Tobin, Jared <TobinJR at dfo-mpo.gc.ca> wrote:
> The responses are much appreciated, thanks.
>
> findstr works and saves a lot of time.  I didn't however have much 
> success with that exact code persay; I get an error message that I 
> don't understand, as follows:
>
> > c1 <- read.fwf(pipe("findstr /b 5 my.file"), ...)
> Error in readLines(con, n, ok, warn, encoding) :
>        'con' is not a connection
> Error in close(file) : no applicable method for "close"
>
> I did however have success with pipe using readLines, albeit in a very

> clumsy fashion:
>
> > c1 <- readLines(pipe("findstr /b 5 my.file")) write(c1, 
> > file="temp.dat")
> > t1 <- read.fwf("temp.dat", ...)
>
> Do you receive the same error message as above when using pipe with 
> read.fwf?
>
> --
>
> jared tobin, student research assistant dept. of fisheries and oceans 
> tobinjr at dfo-mpo.gc.ca
>
> -----Original Message-----
> From: Gabor Grothendieck [mailto:ggrothendieck at gmail.com]
> Sent: Tuesday, May 29, 2007 10:51 PM
> To: Charles C. Berry
> Cc: Tobin, Jared; r-help at stat.math.ethz.ch
> Subject: Re: [R] Partially reading a file (particularly)
>
> On 5/29/07, Charles C. Berry <cberry at tajo.ucsd.edu> wrote:
>
> On windows XP we can also use findstr which comes with Windows:
>
>         res <- read.fwf( pipe( "findstr /b 5 my.file" ) , <other args>
> )
>