In the Aggregated Variables step, select the Variables to be aggregated (3). The Item Statuses table (4) shows which items have been selected, and can be used to filter the Variable list to matching items.
Selected Variables must have the correct Unit so that Models can match them correctly to the target items. The below section explains several ways to set up these Variables.
Creating Variables with the correct Unit for Aggregation
Each aggregated Variable must have a Unit which has been modified to match one of the child items of the Aggregation Variable.
For instance, in the above example, the Aggregation Variable (All costs by cost type) has a Unit of GDP and a Dimension of Cost type, which has seven children (Central staff, Gym staff, etc.).
To match a Central staff Variable, we need a Variable with a Unit of GDP which has had a Central staff modifier applied. To match a Gym staff Variable, we need a Variable with a Unit of GDP which has had a Gym staff modifier applied, and so on for each item.
The screenshot below shows such Units for the Central staff and Gym staff items.
Variables with modified Units for Aggregation
Manual creation
These Variables can be created manually. In this case, the Unit should be specified with appropriate modifiers added, in the Unit step of the Variable wizard, as demonstrated in the gif below.
Setting a Unit Modifier
Read here to understand more about Unit Modifiers.
Automatic creation
If you have not already created the Variables to be aggregated, you can automatically create them in the Aggregated Variables step of the Variable dialog.
To do so, perform the following steps, shown in the example screenshots below:
Navigate to the Aggregated Variables step
Select any items that you want to create in the Item statuses(1). By default, all items will be selected. Selected items are indicated by the filter icon.
Press the Create selected button (2)
A Variable for each item will be automatically created, each with a correctly modified Unit (3)
These new Variables should then be selected and edited as desired
Example of automatic aggregated Variable creation
Aggregating Variables with Dimensions
You can aggregate Variables which themselves have Dimensions, if some or all of the child items of their Dimension are present in the Aggregation Variable.
The screenshot below shows an example of this feature. In this case, the All costs by cost type Variable references a Variable (1) called Costs: Recurring, which has the Simple recurring cost type Dimension applied.
The Simple recurring cost type Dimension has four cost items as children: Marketing cost, Rent, Equipment, and IT & Technology(2). Each of these four items are also present in the Cost type Dimension that is applied to All costs by cost type. Hence selecting Costs: Recurring means that Models is able to determine values for those four items, as indicated in the Item statuses control (3).
In this case, you do not need to apply any Modifiers to the Unit of Costs: Recurring.
Costs: Recurring already has Unit GBP, and the relevant Modifiers are applied in the background by the Simple recurring cost type Dimension
Example of an Aggregation referencing a Variable with a Dimension
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