Update

Update statements show how changes in coefficients are related to changes in variables. The update formula is just the change form of the formula for a coefficient in terms of the levels value of model variables.

Examples:

Update (all,i,COM) HOUSCONS(i) = pCOM(i)*xHOUS(i) ;

Update (change) (all,i,COM) DELB_L(i) = delB + PCOM(i)*delX ;

Update (product) (all,i,SECT) Z(i) = x * y(i) * z ;

Update (explicit) (all,c,COM)(all,r,REG) WEIGHTSX(c,r) = WEIGHTS(c,r);

Product updates are the default, as in the first example.

The right-hand-side of a CHANGE UPDATE can contain any legal expression involving coefficients and variables. However, the right-hand-side of a PRODUCT UPDATE statement can only contain % change variables multiplied together. Each PRODUCT update statement is translated automatically by TABLO into the appropriate algebraic expression. For example,

Update (all,i,COM) DVHOUS(i) = p_PC(i)*p_XH(i) ;

(which by default is a PRODUCT update) is the same as

Update (CHANGE) (all,i,COM) DVHOUS(i) = DVHOUS(i)*[ p_PC(i)/100 + p_XH(i)/100 ] ;

In algebraic terms, both these updates are the same as the algebraic expression:

DVHOUS(i)_Updated = DVHOUS(i)*[1 + p_PC(i)/100 + p_XH(i)/100]

Only real coefficients that are read from file or set by FORMULA(INITIAL) can be updated. Integers and reals declared via COEFFICIENT(PARAMETER) statements may not be updated.

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URL of this topic: www.copsmodels.com/webhelp/tabmate/hc_update.htm

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