Re: st: generate the level series from the growth rate series

[annoporci <annoporci@gmail.com>]

> And your initial values come from where?

I will take 100 as a starting value to create an index.

In the sp500 example, I used the value from the dataset so I could quickly  
check that my calculations were correct, hence:

  replace close2 = 1283.27 in 1

where 1283.27 is the value of "close[_n]" in the dataset.

Thanks.

--
Patrick Toche.


> And your initial values come from where?
>
> Nick
>
> On Thu, Jan 3, 2013 at 11:50 PM, annoporci <annoporci@gmail.com> wrote:
> > Dear Statalist,
> >
> > This must be a very simple question...
> >
> > I have data for percentage changes and would like to reconstruct the
> > levels of the variables.
> >
> > Taking the sp500 dataset, I show below that I can generate the  
> > one-period
> > difference series for the level variable "close", with and without  
> > tsset.
> > Then I try to reverse-engineer to recover the level variable "close"  
> > from
> > the difference series named "change", but I get stuck.
> >
> > sysuse sp500
> > gen change2 = close-close[_n-1] /// method without tsset
> >
> > gen t=_n
> > tsset t
> > gen change3 = close-L.close /// method with tsset
> >
> > gen close2 = .
> > replace close2 = 1283.27 in 1 /// assign the first value
> > replace close2 = close2[_n-1]+change /// try to recover the level
> >
> > This last step fails.
> >
> > I'd appreciate your help very much.
> >
> > --
> > Patrick Toche.
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