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Alias<br />
One device used in the economic equilibrium formulation is the so called alias command that<br />
allows us to have a second name for the same set allowing us in that case to consider both the<br />
effects of own and cross commodity quantity on the demand and supply price for an item. Then<br />
general form of an Alias is<br />
ALIAS(knownset,newset1,newset2,...);<br />
where each of the new sets will refer to the same elements as in the existing knownset.<br />
More on alias appears in the Sets chapter.<br />
Data entry<br />
GAMS provides for three forms of data entry. These involve PARAMETER, SCALAR and<br />
TABLE formats. Scalar entry is for scalars, Parameter generally for vectors and Table for<br />
matrices. Above I needed data for vectors and matrices but not a scalar. Nevertheless I will<br />
cover all three forms.<br />
Scalars<br />
SCALAR format is used to enter items that are not defined with respect to sets.<br />
scalar item1name optional labeling text /numerical value/<br />
item2name optional labeling text /numerical value/<br />
... ;<br />
Examples include<br />
scalar dataitem /100/;<br />
scalar landonfarm total arable acres /100/;<br />
scalars landonfarm /100/<br />
pricecorn 1992 corn price per bushel /2.20/;<br />
Scalars are covered in more depth in the Data Entry chapter.<br />
Parameters<br />
Parameter format is used to enter items defined with respect to sets. Generally parameter format<br />
is used with data items that are one-dimensional (vectors) although multidimensional cases can<br />
be entered. The general format for parameter entry is:<br />
Parameter itemname(setdependency) optional text<br />
/ firstsetelementname associated value,<br />
secondsetelementname associated value,<br />
Courtesy of B.A. McCarl, October 2002 28
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