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Re: st: Calculate product from two dta files


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Calculate product from two dta files
Date   Wed, 7 Nov 2012 10:23:58 +0000

You asked this yesterday and no-one wanted to wrap their head around it.

As I understand it you seek here not just one product price * share
but several, so if each file is already too big for comfort, what
structure precisely are  you seeking?

There are some small things you can do:

1. Your dates are being held as values like 19700701. If that's a
string or a large integer, convert to Stata daily dates, so that for
example 19700701 if stored as a string or long could be stored as an
int instead, a storage saving of 75% for that variable.

2. -compress- anyway. It will do no harm.

There is really one solution here (other than Stata grinding exceedingly slow):

It seems to me that you need more memory. I am guessing that this is
the start of a project and you are doing early basic manipulations.
You've not even started on the serious statistical analysis. You are
going to be hitting this problem again and again. You need to talk to
your boss(es)/supervisor/advisor.

It's still true that you have an inadvisable data structure. I have
asserted this twice before. If you had a long data structure, then the
product price*share would just be one multiplication. That wouldn't
solve your memory problem, however.

Nick


On Wed, Nov 7, 2012 at 9:31 AM, Zhangqunzi <zhangqunzi@googlemail.com> wrote:

>> I have two dta files having the same structure :
>>
>> Dta1
>> time firm price 1 2 3 4
>> 19700701.   0.1.   12.  14.  3
>> Dta2
>> Time firm share 1 2 3 4
>> 19700701.    10   20. 30. 40
>>
>> I want to get the product of price*share then generate a new dat file to store the result.
>>
>> The varlists from dta1,2 are not the same, eg p1 p3 p5. S1 S3 S5. Also the numbers are not continuous numbers.
>>
>> Also my cimputer's memory is not enough only 730mb, the two dtas are 600mb, if u calculate the product in one dta file it will exceed the memory limit.
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