Different lag lengths in a VAR model

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Marqito
Posts: 2
Joined: Fri Dec 07, 2012 12:21 pm

Different lag lengths in a VAR model

Postby Marqito » Fri Dec 07, 2012 12:40 pm

Hi!
Im doing a VAR(9) model and I was wondering if it is possible to have different lag length on each variable. And if so, how do I create my VAR-model with different lag.
Example: I have x1, x2, x3, x4, x5, x6, x7, x8, x9.
And I want a VAR model with:
x1=x1t-1+ x2t-1+ x3t-1+ x4t-1+ x5t-1+ x6t-1+ x7t-1+ x8t-1+ x9t-1+ x1t-2+ x2t-2+ x3t-2+ x4t-2 + x1t-3+ x2t-3+ x3t-3+ x4t-3+ x5t-3+ x6t-3+ x1t-4+ x2t-4+ x3t-4+ x4t-4+ x5t-4+ x6t-4+c
x2= x1=x1t-1+ x2t-1+ x3t-1+ x4t-1+ x5t-1+ x6t-1+ x7t-1+ x8t-1+ x9t-1+ x1t-2+ x2t-2+ x3t-2+ x4t-2 + x1t-3+ x2t-3+ x3t-3+ x4t-3+ x5t-3+ x6t-3+ x1t-4+ x2t-4+ x3t-4+ x4t-4+ x5t-4+ x6t-4+c
x3= x1=x1t-1+ x2t-1+ x3t-1+ x4t-1+ x5t-1+ x6t-1+ x7t-1+ x8t-1+ x9t-1+ x1t-2+ x2t-2+ x3t-2+ x4t-2 + x1t-3+ x2t-3+ x3t-3+ x4t-3+ x5t-3+ x6t-3+ x1t-4+ x2t-4+ x3t-4+ x4t-4+ x5t-4+ x6t-4+c
x4= x1=x1t-1+ x2t-1+ x3t-1+ x4t-1+ x5t-1+ x6t-1+ x7t-1+ x8t-1+ x9t-1+ x1t-2+ x2t-2+ x3t-2+ x4t-2 + x1t-3+ x2t-3+ x3t-3+ x4t-3+ x5t-3+ x6t-3+ x1t-4+ x2t-4+ x3t-4+ x4t-4+ x5t-4+ x6t-4+c
and so on.
In practice this is not impossible to do, but I don’t understand how I can do it in eviews.
Thanks for the help!

EViews Gareth
Fe ddaethom, fe welon, fe amcangyfrifon
Posts: 13604
Joined: Tue Sep 16, 2008 5:38 pm

Re: Different lag lengths in a VAR model

Postby EViews Gareth » Fri Dec 07, 2012 2:02 pm

It is not possible using the built in VAR object. You can, however, use a System object to do it. I would start off by building the VAR (with same lag lengths), then use the Proc->Make System option to build a system object, then manually edit the system to knock off the unwanted lag parts.

The downside is that you won't get to be able to use the built in VAR features (notably impulse responses).

Marqito
Posts: 2
Joined: Fri Dec 07, 2012 12:21 pm

Re: Different lag lengths in a VAR model

Postby Marqito » Mon Dec 10, 2012 1:37 am

I build the VAR with lagg 4, then i go to Proc-> make System option, but then i get order by variable, order by lag... what shall i do then? how do i manually edit the system to know of the unwanted lag parts?

EViews Gareth
Fe ddaethom, fe welon, fe amcangyfrifon
Posts: 13604
Joined: Tue Sep 16, 2008 5:38 pm

Re: Different lag lengths in a VAR model

Postby EViews Gareth » Mon Dec 10, 2012 5:20 am

Choose either.


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