[R] reading and parsing gzipped files

[Prof Brian Ripley]

On Thu, 4 Sep 2008, Dmitriy Skvortsov wrote:

> Hi all,I have  large  compressed text tab delimited  files,
> I am trying to write efficient function to read them,
> I am using   gzfile()  and readLines()
>
> zz <- gzfile("exampl.txt.gz", "r")  # compressed file
> system.time(temp1<-readLines(zz ))
> close(zz)
>
> which work fast, and create vector of strings.
> The problem is to parse the result, if  I use strsplit  it takes longer then
> decompress file manually , read it with scan and erase it.
>
> Can anybody recommend  an efficient way of parsing large vector  ~200,000
> entries

'parse'?  What is wrong with using read.delim (reading 'tab delimited 
files' is its job)?  It (and scan) work with gzfile connections, so there 
is no need to decompress manually.

See the 'R Data Import/Export Manual' for how to use read.delim efficiently.

> Dmitriy
>
> 	[[alternative HTML version deleted]]
>
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> and provide commented, minimal, self-contained, reproducible code.

PLEASE do.


-- 
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)
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