Unit Factors

How to move between different "sizes" of Unit

Overview

It is common for models to change between different "sizes" of unit.

For instance, a financial model for a large company may have a "standard monetary unit" of $000. This means that, unless otherwise specified, all monetary figures are in thousands of US dollars.

Some Variables may need to be specified in a different unit, e.g. the price of a product may be in single US dollars ($).

Unit Factors in Models allows you to move between different factors within the same Model, without needing to specify different versions of the same Unit.

Defining Unit Factors

Factors are applied to individual Unit Parts. When a Factor has been applied, it will be shown in brackets alongside the unit type, for example GBP (000) as shown in the screenshots below.

To edit the Factor, click on the Unit within the Unit Part (1), which will bring up a Unit editor popup, within which you should click the "More" button (2). This will open a new wizard step in which you can edit both the base Tag of the Unit Part and the Unit Factor (3).

Shortcut to bring up the Unit editor

The "More" button of the Unit editor

Choosing a Unit Factor

Moving between Unit Factors in Calculations

Factors will be assessed by Models when analysing whether Calculations are consistent.

Models will show warnings if:

1. A Calculation produces a factor that is different from that of the specified Unit

2. You try to sum together items with different factors

These warnings, and their remedies, are described in the following sections.

Factor matching error

The screenshots below show an example of how Models deals with a change in Unit Factors. In this case, we have a Variable, Total revenues of Unit GBP. A second Variable, Total Revenues (000s) (1), has a Calculation that simply references the first Variable, but its Unit is in GBP (000s).

Models detects that the Calculation Unit (GBP) does not match the target Unit of GBP (000s), so shows a warning. Models provides two options: Apply Factoring? (3), and Override unit error? (4).

If Apply Factoring? is checked, the Calculation is automatically divided by 10^3 = 1000 (5), and a tick mark (6) shows that the Variable Unit is now correct.

Selecting the Override unit error? option will remove the error, but the calculation will need to be modified manually. We recommend using the automatic factoring where available.

Error before Factoring applied

Error after Factoring applied

Addition error

The screenshot below shows the result of adding together (or subtracting) items with different Unit Factors. In this case, we have a Variable, Total Profits (1) whose Calculation is Total Revenues (000s) - Total Costs (2). As Total Revenues (000s) has Unit GBP (000s) and Total Costs has Unit GBP, Models is unable to determine the resulting Unit of the Calculation.

Error when adding/subtracting Variables with different factors

In this case, the options are:

1. Manually edit the Calculation and select the Override unit error? option (see warning below)

2. Create a new Variable that converts one of the parts of the Calculation into the correct Factor first before using it in the Calculation (recommended).

We strongly encourage you to use option 2 where possible. This will aid clarity of your Model and help other users understand the flow, while ensuring that you do not make a mistake manually converting between factors.