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

 From annoporci To statalist@hsphsun2.harvard.edu Subject Re: st: generate the level series from the growth rate series Date Fri, 04 Jan 2013 14:32:30 +0800

```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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