Page 1 of 1
using @cumsum(x(-1) in a regression/forecast model for x
Posted: Wed Aug 11, 2010 4:11 pm
by LAO
Hello,
I am modeling a variable whose value should depend on a function of its lagged cumulative sum.
Does regressing x on c @cumsum(x(-1)) behave the way I want it to, that is, are predicted values of x summed up, when forecasting?
-James
Re: using @cumsum(x(-1) in a regression/forecast model for x
Posted: Wed Aug 11, 2010 4:13 pm
by startz
No, the actual values of x, added up, are used for forecasting.
Re: using @cumsum(x(-1) in a regression/forecast model for x
Posted: Wed Aug 11, 2010 4:21 pm
by LAO
I was worried that would be the case. Do you have any ideas on how I can add up and use the predicted values as the forecast rolls ahead?
Re: using @cumsum(x(-1) in a regression/forecast model for x
Posted: Wed Aug 11, 2010 4:34 pm
by startz
I missed something. You said that the left hand side variable is x. In that case a dynamic forecast may in fact do what you want. You might want to try out a simple example to see what happens.
(Either that or hope Gareth or Glenn intervene

)
Re: using @cumsum(x(-1) in a regression/forecast model for x
Posted: Wed Aug 11, 2010 4:42 pm
by EViews Gareth
Startz's first answer is correct - the actual values will be added up, I believe. I don't think the forecast engine knows what to do with @cumsum.
The only work around is to create a model and solve the model over the forecast period. The model would look something like this:
where Y is a temporary series you've created in the workfile, and c(1) and c(2) are the coefficients from your equation (you can just type the values in manually)
Re: using @cumsum(x(-1) in a regression/forecast model for x
Posted: Wed Aug 11, 2010 4:47 pm
by LAO
Thank you.