[R] gzfile() produces large files

[Peter Malewski]

I would guess that this is an artifact of compressionalogor.:

under a unix shell:

 > cat tmp1.txt
1 2 3 > ls -l tmp1.txt
-rw-------   1 y0004379   users            5 Juni 27 17:31 tmp1.txt
 > gzip tmp1.txt
 > ls -l tmp1.txt.gz
-rw-------   1 y0004379   users           34 Juni 27 17:31 tmp1.txt.gz
 

#####on windows r-1.3.0:

> x <- rnorm(10000)
> write(x, file = "c:/temp.txt")
> system("ls -l c:/temp/temp.txt",T)
[1] "a-----      4093 27-Jun-101 16:50 c:/temp/temp.txt"
> my.con <- gzfile("c:/temp/temp.gz", open = "w")
> write(x, file = my.con)
close(my.con)
> > system("ls -l c:/temp/temp.gz",T)
[1] "a-----    193200 27-Jun-101 17:24 c:/temp/temp.gz"

on large file the gzip - alogorithm is effective!

Peter 


>
 > ls -l tmp1.txt.bz2
-rw-------   1 y0004379   users           43 Juni 27 17:31 tmp1.txt.bz2
 >


On Wed, Jun 27, 2001 at 03:11:37PM +0100, Prof Brian D Prof Brian D Ripley wrote:
> On Wed, 27 Jun 2001, Uwe Ligges wrote:
> 
> > I observed some strange results playing around with gzfile() [R-1.3.0,
> > WinNT 4.0]:
> >
> > At first
> >
> >   x <- 1:1000
> >   write(x, file = "c:/temp.txt")
> >
> > results in a file of about 4 kB. But
> >
> >   my.con <- gzfile("c:/temp.gz", open = "w")
> >   write(x, file = my.con)
> >   close(my.con)
> >
> > results in a file of about 16 kB.
> >
> > I expected a reduction of the size. Anyone who can tell me what went
> > wrong?
> 
> My experiments concur: I do get a 15913 byte file and it is a valid gzip
> file.
> 
> I've used this much more to read compressed files than write them.
> I will take a closer look at the zlib specs when I have time.
> 
> Brian
> 
> -- 
> 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 272860 (secr)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> 
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-- 
P.Malewski, Limmerstr.47, 30451 Hannover, 0511-2135008
At work: http://www.MH-Hannover.de 0511 532 3194 / Fax: 0511 532 3190, 
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