> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Nick Cox
> Sent: 17 April 2003 09:11
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: RE: RE: Calculating running cumulative totals (2)
>
>
> Adam Chapman
>
> > > > I'm trying to calculate a running cumulative total for
> > > observations over
> > > > the previous 12 months (cum12month). My data looks like:
> > > >
> > > > # Obs Month Cum12month
> > > > 2 1 2
> > > > 4 2 6
> > > > 3 3 9
> > > > 1 4 10
> > > > 2 5 12
> > > > 4 6 16
> > > > 2 7 18
> > > > 1 8 19
> > > > 5 9 24
> > > > 3 10 27
> > > > 2 11 29
> > > > 4 12 33
> > > > 5 13 36
> > > > 2 14 34
> > > > 3 15 34
> > > > 2 16 35
> > > > 4 17 37
> > > > etc
>
> Nick Cox
>
> > gen Cum12month = sum(Obs)
> > replace Cum12month = Cum12month - Cum12month[_n-12] if month > 13
>
> Another way:
>
> tsset month
> gen Cum12month = sum(Obs) - sum(L12.Obs)
>
> Both these methods extend to panel data. The second is more
> easily done (and works better if there are gaps):
>
> tsset id month
> gen Cum12month = sum(Obs) - sum(L12.Obs)
Meaning (!)
bysort id (month) : gen Cum12month = sum(Obs) - sum(L12.obs)
Nick
n.j.cox@durham.ac.uk
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