st: RE: why -recode-takes longer than -replace-

["Martin Weiss" <martin.weiss1@gmx.de>]

<>


BTW, Amanda, you may also want to upgrade to MP 11.1, which gives you even
better timings. In my case, with 4 cores, the -replace- advantage is almost
95%. 

See also the latest installment of http://www.stata.com/statamp/statamp.pdf,
pages 105/106, where -replace- profits from MP much more than -recode-. 


HTH
Martin


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Amanda Fu
Sent: Sonntag, 27. Juni 2010 22:11
To: statalist@hsphsun2.harvard.edu
Subject: st:why -recode-takes longer than -replace-

Dear Statalisters,

I am just curious about a fact noticeable when I use -recode- (1 as
following) or -replace- (2 as following)  to recode all the variables
in a data set (size :  52,996,616) using Stata 10.1 SE: the recode
command  takes much longer than replace. I was wondering what causes
the speed difference and if the speed difference implies for large
data set it would be better to use replace instead of recode.

1.  slower
.recode _all (8=.) (9=.)

2. faster
foreach v of varlist * {
.replace `v'=. if `v'==8 | `v'==9
}
end

Thanks for your time!

Sincerely,
Amanda
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