Re: st: superposed rolled windows

[Jeph Herrin <junk@spandrel.net>]

I thought the poster was unambiguous about wanting to change
the database in the strong sense - he exhibits a "New data base"
which does not contain observations for years where there are
no forward values.

Though as long as he is content with the results, I suppose
any ambiguities - his, mine, yours - are irrelevant, eh?

thanks,
Jeph

Nick Cox wrote:
> I was ambiguous, but in a way often 
> used in Stata circles. 
> Changing the data in the strong sense
> includes -drop-ping observations, as 
> this is irreversible, unless by 
> going back to the original dataset. 
> Changing the data in the weak sense
> includes any -generate- of a new
> variable. That is reversible, as
> the new variable can be -drop-ped
> and re-created at will assuming 
> no changes of the data in the 
> strong sense. 
> Others have explained F. 
> Nick 
> n.j.cox@durham.ac.uk 
> Jeph Herrin
>  
> > According to his original post, he wanted to change
> > his data. But the point about the gaps is well taken.
> >
> > what is "F."? other than the F density.
> Nick Cox wrote:
>
> > > This changes your data and assumes no 
> > > gaps. Using -tsset- and F. is a  
> > > better way to do it. 
> Jeph Herrin
>   
> > > > Try
> > > >
> > > >   gen profits1=profits
> > > >   bys firms (years): gen profits2=profits[_n+1]
> > > >   bys firms (years): gen profits3=profits[_n+2]
> > > >   drop if profit2==.
> > > irodriguez
> > >
> > > > > i need to generate some columns data in excel I think I 
> > > > could calculate 
> > > > > them in stata
> > > > > I have a panel data with firms, and profits for the period 
> > > > 1990/2004 No 
> > > > > all the firms have the same period of data
> > > > > I need to calculate others 4 columns for profit
> > > > > superposing a rolling period window of 3 periods.
> > > > > Example:
> > > > > original data base
> > > > > Firms    Years   Profits   
> > > > > firm 1     1990     7
> > > > > firm 1      1991     9
> > > > > firm 1      1992      2
> > > > > firm 1      1993       6
> > > > > firm 1       1994      5    
> > > > > firm 1       1995     4
> > > > > firm 2      1990      3
> > > > > firm 2      1991      2
> > > > > firm 2      1992      1
> > > > > firm 2       1993     3
> > > > > ...
> > > > >  
> > > > > New data base
> > > > > Firms    Years   Profits1    Profit2   Profit3   
> > > > > firm 1     1990     7                9         2
> > > > > firm 1      1991     9               2         6
> > > > > firm 1      1992      2              6         5
> > > > > firm 1      1993       6            5          4
> > > > > firm 2      1990      3             2           1
> > > > > firm 2      1991      2              1          3
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