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st: Re: Saving 1 observation


From   "Michael Blasnik" <michael.blasnik@verizon.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: Saving 1 observation
Date   Wed, 28 May 2008 19:14:48 -0400

...

I have two suggestions that may be worth exploring:

1) use -restore, preserve- instead of -restore- and you will save the time required to preserve the dataset next time.

2) a little more tricky, but you could employ -post- to post an observation to a dataset. I'm not sure how much time this would save but it may be worth a try.

Michael Blasnik


----- Original Message ----- From: "Sergiy Radyakin" <serjradyakin@gmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Wednesday, May 28, 2008 6:31 PM
Subject: st: Saving 1 observation



Hello All!

I have a large dataset (to be specific ~ 1mln observations, 600MB).

I need to (repeatedly) save several small portions of it (small can be
as small as 1 observation) into separate files.

So far it is done similarly to this

preserve
 keep if Needed1
 save "Portion1"
restore

preserve
 keep if Needed2
 save "Portion2"
restore

... etc ...

where variables Needed1 and Needed2 are dummies generated earlier in the code.

This works. But it is painfully slow.

The problem is that it will necessarily have to preserve/restore the
whole large dataset.
-save-  does not support -if- and -in- modifiers, otherwise my ideal
choice would be:

save "Portion1" if Needed1
save "Portion2" if Needed2

As an alternative I was thinking of saving the dataset directly (by
generating Stata file byte-by-byte), but since I need labels to be
preserved together with the data, this becomes more tricky, and
reinventing what is already [well] done, does not sound like a good
idea.

To pose a specific question: how to save one observation 1<=K<=_N
(with labels) to a Stata file, without having to save the whole
dataset?

Version of Stata: Stata 10/ Windows

Thank you,
   Sergiy Radyakin
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