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Re: st: How to set a year index?


From   Oliver Jones <ojones@wiwi.uni-bielefeld.de>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to set a year index?
Date   Fri, 20 May 2011 17:12:51 +0200

On 20.05.2011 16:58, Nick Cox wrote:
The logic here is fine, but why do it this way?

summarize price if year == 2005, meanonly
gen price_index = price/r(mean)

Note how

1. The middle macro is completely unnecessary.

I used the macro to make the code more readable/understandable.


2. Although it will not usually bite, you are probably losing asmidgen of precision by using a local.

Good point! I'm not sure, but I think the use of a scalar can solve the precision
problem of the local. So my code would be

scalar base_value = r(mean)
gen price_index = price/base_value


3. Specifying -meanonly- is efficient if all you need is the mean.


I'm not an expert on computing efficiency, but I wouldn't expect to
see a difference in execution time when -summarize-ing one single
observation.
But I admit that it is good style to use the meanonly option.

Small points indeed, but in computing the devil is often in the details.

Nick
n.j.cox@durham.ac.uk
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