[R] Scanning data files line-by-line
Prof Brian Ripley
ripley at stats.ox.ac.uk
Wed Apr 30 15:13:26 CEST 2003
On Wed, 30 Apr 2003, R A F wrote:
> Maybe I'm missing something. When I do readLines( "file", n = 1) and
> repeat, it always reads the first line of "file". I've to be able to
> advance to the next line, no?
You need to open the connection first. readLines( "file", n = 1)
opens file "file", reads a line and then closes "file". It has no idea
that you want to keep reading the same file.
> I'll take a look at the command file(), as someone else suggested.
It's open() you need, as in
con <- file("file")
for(i in 1:10) print(readLines(con, n=1))
In C you would need to (f)open a file to read it line-by-line, just as
The first two lines can be collapsed to
con <- file("file", "r")
> >From: Duncan Murdoch <dmurdoch at pair.com>
> >To: "R A F" <raf1729 at hotmail.com>
> >CC: R-help at stat.math.ethz.ch
> >Subject: Re: [R] Scanning data files line-by-line
> >Date: Wed, 30 Apr 2003 08:26:26 -0400
> >On Wed, 30 Apr 2003 11:51:00 +0000, you wrote:
> > >Hi all, is there a way to read a data file into R line-by-line, akin
> > >to what fscanf does in C, say?
> > >
> > >It seems that "scan" and "read.table" both read the entire data file
> > >in at once, whereas "readLines" allows one to read a file partially,
> > >but doesn't quite read line-by-line either.
> >That's what readLines(con, n=1) is supposed to do; in what way does it
> >not quite work?
> R-help at stat.math.ethz.ch mailing list
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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