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Re: st: adding variables to a new data file


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: adding variables to a new data file
Date   Tue, 12 Feb 2013 22:37:32 +0000

My point is the same. Just to add that there's a convenience command
on SSC, -savesome-.

Nick

On Tue, Feb 12, 2013 at 10:31 PM, Steve Nakoneshny <scnakone@ucalgary.ca> wrote:

> It isn't clear to me why you would need a loop in the first place to identify your variables of interest. Is the size of your dataset a limiting factor due to your version of Stata? Can you not simply keep a running tally of the variables you want to keep and export them en masse?  Perhaps through the judicious use of a do file?

On 2013-02-12, at 3:21 PM, David Epstein wrote:

>> This must be a really easy question to answer, but I'm feeling
>> stumped. I have a data set with a large number of variables in it. I
>> want to create a new data set with a subset of those variables, with
>> the exact variables to be exported being read off a loop a few
>> variables at a time.
>>
>> So for instance I first want to export the key identifying variable,
>> which in my case is date. So I will:
>>
>> preserve
>> keep date
>> save temp, replace
>> restore
>>
>> Then I'll loop through my loop once and get the names of five
>> variables I want to add to temp, call them v1 v2 v3 v4 v5. The next
>> time through, I'll get variables v6 through v10, and so on until I've
>> added, say 50 variables to temp.
>>
>> My question is, what do my loops look like? Am I merging each time
>> through? Keeping, say, date v1 v2 v3 v4 v5, merging, then restoring? I
>> could, but that seems like it could take a while to keep preserving
>> and restoring all the time. Plus, I keep having to save the temp file
>> and then switch back to the master data set. Isn't there a command
>> that says "take these variables from my current data set and add them
>> to another data set?"

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