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st: RE: How to insert new observation?


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: How to insert new observation?
Date   Tue, 18 Feb 2003 20:19:14 -0000

Zang Hailing

> I am trying to insert new observations into the existing 
> data file. For 
> example, the trading days are only weekdays, namely Monday 
> through Friday. 
> But I also wish to list Sat and Sun in the data file. (So 
> only date appears, 
> other columns will be blank because of no data.)
> 
> for example:
> 08/01/2001 --Wed
> 08/02/2001 --Thu
> 08/03/2001 --Fri
> 08/05/2001 --Mon
> 
> I wish to have 08/04/2001 and 08/05/2001 appears to be able 
> to merge with 
> other data sets. How can I do that?

One way is to add them at the end of the data and then -sort- 
them into order. But if you are doing this for many such 
weekends, that is no fun, and indeed error-prone. 

An alternative is to create a data file with all the days you 
need and -merge-. 

Suppose I want all the days from 1 Jan 1970 to 31 Dec 2004. 

. di mdy(1,1,1970) 
3653

. di mdy(1,1,2005) 
16437

. di 16437 - 3653 
12784

I need a data set (a date set) 

. set obs 12784 
. gen day = _n + 3652 
. format day %d 

Now -save- and -merge- with the holey data set. 

You need to watch for the fencepost problem (being 
off by one). 

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