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Question regarding first differences

Posted: Mon Mar 24, 2014 5:23 am
by Christian_87
Hello

At the moment I am building an AR(2) modell (times series) were I have a produced a forecast. To achive stationarity I had to take the log first differences of my variables before making the forecast. The forecast has given me forecasted first differences values. My question is how do I recalculate the forecasted values back to its "original values"? I have tried a thing like x1+x1(+1) ( the opposite of first differnces, but it doesent work.)

Thanks in advance!

Re: Question regarding first differences

Posted: Mon Mar 24, 2014 6:35 am
by startz
If you make your forecast variable d(x), instead of defining a new variable equal to d(x), EViews will forecast x for you.

Re: Question regarding first differences

Posted: Tue Mar 25, 2014 1:28 am
by Christian_87
Thanks for the quick answer!

Iam not shore of what you are meaning exactly. So if I get a forecasted variable that is log diff, should i transform the forecasted variable log diff to its original value? Or is their some kind of function in Eviews that i should use?

Re: Question regarding first differences

Posted: Tue Mar 25, 2014 6:27 am
by startz
Try the following regressions and then forecasting from each to see what variables are created by the forecast.

Code: Select all

ls d(x) c z ls dlog(x) c z

Re: Question regarding first differences

Posted: Wed Mar 26, 2014 2:33 am
by Christian_87
Thanks!

It works now!