st: Re: differencing

[Kit Baum <baum@bc.edu>]

Yes. A oft-biting bug is to have observations

year       y
1998    123
1999    144
2001    192
2002    201
...

and use y[_n-1] to refer to a lagged value. That is perfectly  
computable, but not what you mean for 2001; the lag and difference  
should be undefined. You can have gaps in time series with tsset; it  
is the individual commands that are used after that where issues of  
gaps may (or may not) arise. But the use of L. and D. is a great  
safety feature to ensure that any inadvertent errors in the time  
variable will become immediately apparent.

Kit Baum, Boston College Economics
http://ideas.repec.org/e/pba1.html


On Nov 15, 2005, at 2:33 AM, Eric wrote:


> If I understand the tsset stuff at all, that approach would force  
> Gregor to come to terms with any date gaps & duplicate years which  
> my approach glosses over.  Is that right?
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