Creating a Variable
Description
To create a new variable in the Model Tree:
Select the position in a Declaration Section where the new variable should be inserted
From the Edit menu select Insert – Variable
Enter a name for the new variable (if you are creating a multi-dimensional variable, you can type the indices of each dimension as well)
Press
<Enter>
to create the new variable (or press<Esc>
to abort the operation)
The newly created variable is now ready for use, but you probably want to specify some additional attributes. To modify the attributes of the newly created variable:
Press
<Enter>
or double click on the variable node.
The most commonly used attributes of a variable are discussed below.
INDEX DOMAIN
: TheINDEX DOMAIN
attribute should be specified in order to declare indexed variables. Thewizard will display the Set Dependency Tree of your model and allows you to select one or more indices.
RANGE
: TheRANGE
attribute should be specified in order to restrict the values to certain intervals. Thewizard will let you either select one of the predefined ranges, like
Real
,Nonnegative
,Nonpositive
,Integer
, orBinary
, or specify a (parametric) interval range.UNIT
: TheUNIT
attribute is used to specify the unit in which the variable’s value is measured. By specifying a unit, AIMMS is able to perform automatic unit conversions and unit consistency checks. Thewizard will let you select a unit and quantity from the list made up from your model quantities and units together with the information in the AIMMS SI unit base.
DEFAULT
: TheDEFAULT
attribute should be used in order to specify a nonzero default value for the variable. Note that AIMMS will explicitly store all values that are non-default.PROPERTY
: ThePROPERTY
attribute should be used to specify additional properties. Note that in order to retrieve sensitivity information from the solver, theReducedCosts
,ValueRange
, orCoefficientRange
property should be explicitly set. Thewizard will let you specify the properties through a selection of radio buttons and check boxes.
DEFINITION
: TheDEFINITION
attribute for variables can be used specify a constraint that defines the value of the variable. Instead of specifying the constraint explicitly and adding it the constraint set of the mathematical program, AIMMS will generate additional constraints based on theDEFINITION
attribute as needed.
Learn more about