Furthermore, calculating the sums in float format isn't as bad as it initially seems: the fact that Stata shows only 3 digits of precision has to do with the display format. The float is precise up to 8 digits, and is stored that way, as can be seen in the program below.
*-------------------------example------------------
drop _all
input x
42224464
67090781
end
egen sum = sum(x)
egen long sumlong = sum(x)
list sum sumlong
format sum %20.7g
list sum sumlong
*------------end example-----------------
HTH,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of Nick Cox
Sent: maandag 28 november 2005 16:42
To: [email protected]
Subject: st: RE: generating a new variable with the egen command
Your call should be
egen double newvar = ...
or
egen long newvar = ...
If these are integers, -long- is better. Either type
is allowed by the syntax. See the help for -egen- once more.
Nick
[email protected]
>[email protected]
>
> I'm trying to generate a new variable given by the sum of an
> existing variable
> by year (as I have 2 six month observations for the same
> year) and individual.
> The command is the following:
> egen newvar=sum (oldvar), by(id year)
>
> the problem is that the original values are, for instance:
> 42224464 and
> 67090781, but the sum that STATA computes is 109000000,
> instead of 109315245.
> Why does it round like that?
> The old variable is stored as "double", I have tried to
> change the storage
> type, using recast, but STATA does not allow to do it, as
> many values would be
> changed...
*
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* http://www.stata.com/support/faqs/res/findit.html
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