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Re: st: calculating the difference in logs


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: calculating the difference in logs
Date   Thu, 12 Jul 2012 14:00:08 +0100

Time series operators work on variables, not expressions in general, so I don't think there is a short-cut of the kind you seek.

Nick

On 12 Jul 2012, at 13:47, "Data Analytics Corp." <walt@dataanalyticscorp.com > wrote:

Hi,

Suppose I have a time series on annual sales. I'd like to calculate the year-over-year percent change using the difference in the natural logs. I tried

   g pct = d.ln(sales)

but I got an error message "unknown function d.ln()"

Then I tried

   g logg = ln(sales)
   g pct = d.logg

and I got the right answer. I'd like to use just the one line statement as in the first example. Can this be done?
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