Modifying a Decomposition

Occasionally the decomposition of the Formula may not be quite what you want. In this case, it should be reasonably easy to modify the expressions in the memo on the AnalyseGE form and then re-evaluate them, as an example shows.

Example

Consider the formula in ORANIG for calculating V0IMP(c), the total value of imports of commodity c.

Formula (All,c,COM) V0IMP(c) =

SUM{i,IND, V1BAS(c,"imp",i) + V2BAS(c,"imp",i) }

+ V3BAS(c,"imp") + V5BAS(c,"imp") + V6BAS(c,"imp") ;

Suppose you select to decompose the RHS of this formula (putting the toggle first). You will see from the memo on the AnalyseGE form what has been evaluated. The contents of that memo will be as below.

XSet IntDec1 (V1BAS, V3BAS, V5BAS, V6BAS) ;

Coefficient (All,xxi1,IntDec1)(All,c,COM) TempCoeff(xxi1,c) ;

Formula (All,c,COM) TempCoeff("V1BAS",c) =

sum{i,IND,V1BAS(c,"imp",i)+V2BAS(c,"imp",i)} ;

Formula (All,c,COM) TempCoeff("V3BAS",c) = V3BAS(c,"imp") ;

Formula (All,c,COM) TempCoeff("V5BAS",c) = V5BAS(c,"imp") ;

Formula (All,c,COM) TempCoeff("V6BAS",c) = V6BAS(c,"imp") ;

Write ;

You will see that the decomposition has grouped the V1BAS (intermediate inputs) and the V2BAS (inputs to capital creation) values into the same toggle (to which it has given the slightly misleading name V1BVAS). These have been grouped together because the automatic decomposition of formulas (or the intelligent decomposition of equations) leaves brackets intact.

You probably want the V1BAS and V2Bas contributions to V0IMP shown separately. [Of course this would have happened if the start of the RHS in the original Formula had been written as

SUM(i,IND, V1BAS(c,"imp",i)) + SUM(i,IND, V2BAS(c,"imp",i))

with the V1BAS and V2BAS in separate SUMs.]

It is easy to modify the statements above to separate the V1BAS and V2BAS terms. To do so,

•Add toggle V2BAS to the set IntDec1 and change the name of the set to IntDec2 (because AnalyseGE remembers all XSETs and so will object if you try to define another set called IntDec1). Also change all occurrences of IntDec1 to IntDec2.

•Copy the formula for TempCoeff("V1BAS",c) to one for TempCoeff("V2BAS",c), delete the V2BAS term from the first and the V1BAS term from the second.

Then the statements will read:

XSet IntDec2 (V1BAS, V2BAS, V3BAS, V5BAS, V6BAS) ;

Coefficient (All,xxi1,IntDec2)(All,c,COM) TempCoeff(xxi1,c) ;

Formula (All,c,COM) TempCoeff("V1BAS",c) =

sum{i,IND,V1BAS(c,"imp",i)} ;

Formula (All,c,COM) TempCoeff("V2BAS",c) =

sum{i,IND,V2BAS(c,"imp",i)} ;

Formula (All,c,COM) TempCoeff("V3BAS",c) = V3BAS(c,"imp") ;

Formula (All,c,COM) TempCoeff("V5BAS",c) = V5BAS(c,"imp") ;

Formula (All,c,COM) TempCoeff("V6BAS",c) = V6BAS(c,"imp") ;

Write ;

Once you have made these changes, click on the Evaluate button on the AnalyseGE form. This time the V1BAS and V2BAS terms will be shown separately.

[If you need to modify a decomposition, it may help to understand the implementation of toggles in a little detail.]

URL of this topic: www.copsmodels.com/webhelp/analysege/hc_moddecomp.htm

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