Get/Pay Expressions

Get/pay expressions are placed on branches of the decision tree, and are used to tell DPL how to calculate the value functions for each attribute in the model.

Specifying Get/Pay Expressions

You can specify a get/pay expression for a branch directly in the ribbon (Decision Tree | Get/Pay) or the Get/Pay tab of the Branch Definition dialog. See Branch Definition | Get/Pay.

A get expression is added to the value model; a pay expression is subtracted. Although you can only attach one get or pay expression for each attribute to each branch, you can get or pay more than one value for each attribute by using an expression that contains sums or differences of the values. You can enter either simple numerical values or complex expressions as data. You can also enter previously defined variables or use DPL's functions. If you use the name of a node defined in the Influence Diagram as a variable, you must enter it as DPL will use it internally, not as it appears in the node name. See Node Names for information on the possible differences.

If the expression consists of a single variable, use the lower drop-down in the Decision Tree | Get/Pay group to select it. If the expression contains more than one variable or functions, use the Select Variable button or Select Function button either on the ribbon or within the dialog. Select the appropriate variable or function from the dialog and click OK.

If you have multiple attributes in a model, then you must enter an expression for each attribute on every branch where you specify a get/pay expression. If you need to enter a get/pay expression on a branch where only one attribute is affected, use zeroes as placeholders for the attributes not affected. E.g., assume you had a two-attribute model with attributes Schedule and Cost. If for a particular chance node (call it Chance1) the outcome of it affected Cost but not Schedule, you would enter 0 for the first attribute and Chance1 for the second attribute for that branch.

If the node is symmetric (i.e., the branches have one common endpoint), the get/pay expression will be attached to all the branches. If the node is asymmetric or mixed, you may enter different get/pay expressions for each separate branch or group of branches.

DPL needs to associate some number with each path through the tree. If you run a model which doesn't contain any get or pay expressions, DPL will warn you and ask you for an expression.

Hiding Get/Pay Expressions or Displaying an Indicator

The get/pay expression is displayed under the branch at the right end of it on the diagram. If you wish to hide the get/pay or display only an indicator ($), you may do so by selecting the branches and changing the setting within Decision Tree | Get/Pay group.

Versions: DPL Professional, DPL Enterprise, DPL Portfolio