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Re: st: Saving data in compressed format? - wishlist...


From   "Stephen P. Jenkins" <stephenj@essex.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Saving data in compressed format? - wishlist...
Date   Thu, 13 Feb 2003 10:54:15 +0000 (GMT Standard Time)

On Wed, 12 Feb 2003 19:37:56 -0000 "Cruces,GA  (pgr)" 
<G.A.Cruces@lse.ac.uk> wrote:

> Dear All,
> 
> As you might have noticed, "zipping" a .dta file often results in
> compressed files that are less than one tenth of the original file size.
> I couldn't find any documentation on a compressed stata file format - if
> there is, please let me know and ignore the rest of this message. I
> solve the problem of large files (in Windows) by compressing the folder,
> so it uses less disk space, but it is still a problem when you want to
> transfer or transport files.
> I don't really know what it would take, but my guess is that it wouldn't
> be too hard to store the files in some sort of compressed format, and
> having Stata decompressing them on the fly when opening. I could even
> think of having very large datasets (larger than physical memory)
> compressed in memory... but that would probably slow things too much. 
> Since I don't think this will be implemented soon, could someone share
> experiences on invoking Windows apps from within stata? I'm thinking
> about doing some sort of "usezip" program that would open .zip files...
> Thank you!

If you have a (de)compression utility that you can call from the 
DOS command line, then should it not be straightforward to
* keep a compressed version of your file(s)
* call the utility from within Stata (prompt or do file) to decompress 
	(commands line prefaced with -!-)
* do your Stata job
* call program again if necessary to compress again.

WinZip, one of the leading shareware compression utilities for Windows, 
has a command line support add-on. See http://www.winzip.com/wzcline.htm
I expect you can do the same with a number of other utilities on 
both Windows and other platforms

Stephen
----------------------
Professor Stephen P. Jenkins <stephenj@essex.ac.uk>
Institute for Social and Economic Research (ISER)
University of Essex, Colchester, CO4 3SQ, UK
Tel: +44 (0)1206 873374. Fax: +44 (0)1206 873151.
http://www.iser.essex.ac.uk



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