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Exogenous Variable Overides in Scenarios

Posted: Thu Jul 28, 2011 8:24 am
by econac
I was having trouble with solving a Model for a non-baseline scenario that was based on a System where one of the exogenous variables was an expression ( d(exog)). I solved this by creating a workfile variable, say exogdif = d(exog), but I was wondering if there was a more efficient way to do this in the Model object. Wasn't sure if the Proc Make Graph Transformation option in the Scenario box would do this or not.

Thanks

Re: Exogenous Variable Overides in Scenarios

Posted: Thu Jul 28, 2011 8:50 am
by EViews Gareth
Hard to know if there is a more efficient method to solve the problem without knowing what the problem was. What "trouble" did you have?

Re: Exogenous Variable Overides in Scenarios

Posted: Thu Jul 28, 2011 11:19 am
by econac
Thanks, Gareth. Sorry, the specific error was that the model would not solve for the endogenous variable who's equation contained the expression d(exog). When I created the new workfile variable exogdiff = d(exog) and replaced that in the system equations and re-linked, the model solved. So generally, when one has an expression-based exog vars in the system for estimation and then solves a model, and then constructs scenarios with overides, it seems like the expression-based exog doesn't "flow through". Could I have listed in the overides, "d(exog)_1" for scenario 1?

Thanks

Re: Exogenous Variable Overides in Scenarios

Posted: Thu Jul 28, 2011 11:29 am
by EViews Gareth
Seems to work for me:

Code: Select all

create u 100
rndseed 1

series y1=nrnd
series x1=nrnd
series x1_1 = 0
series y2=nrnd
series x2=nrnd

system s
s.append y1=c(1)+c(2)*d(x1)
s.append y2=c(3)+c(4)*x2
s.ls

s.makemodel(m)
m.scenario(a=_1, n) "alt"  'create a scenario
m.override x1  'set x1 as the override for the scenario.
m.solve  'solve.  If x1 is being over-ridden, the solution for y_1 should be a constant value.

Re: Exogenous Variable Overides in Scenarios

Posted: Fri Jul 29, 2011 11:54 am
by econac
Thanks. I'll give it a try that way. I was using the menus, but if the code works.....then it can be done! Thanks again, Gareth.