Assigning units

You manually assign units to stocks and converters in the model.

All stocks in a main chain are automatically assigned the same units that you assigned to any stock in the chain.

Units for flows are automatically assigned by the software based on the units you have assigned to their associated stocks. For example, if you assigned a unit of measure called "widgets" to a stock, and your model is running in months, any flows into or out of the stock would automatically be assigned the units "widgets per month," a built in unit definition with equation widgets/month.

Notes: If you add stocks or flows to the chain after you assign units, the new variables will not be automatically assigned units. To assign units to the new variables, assign units to any stock in the chain; everything else in the chain will automatically be assigned units.

If there is a unit-converted flow (one for which the Unit conversion check box is selected) in the chain, any flows or stocks beyond that flow will not be automatically assigned the same unit of measure; you must manually assign units to those stocks yourself.

When you assign units to a variable, you can select from existing units, select from units already used in the model, create new units, or have the software suggest the appropriate units based on the variable's equation.

To assign units

Using the Units options on the Equation panel.

Note: You can also quickly assign existing units by right-clicking the in the stock or converter on the diagram, choosing Units, and then choosing the units you want to assign.

1. Select the stock or in the model diagram.
2. Click the Equation panel.

3. Use the Units box at the bottom of the Equation panel to assign units:

• To assign by typing,start to type the units you want to assign. As you type, existing units that match the letters you type appear in a drop-down list. Use the arrow keys to highlight the units you want to assign, and then press Enter. If the units are not in the list simply type them in.
• To select existing units from a list of categories, click to the right of the Units box, select the category you want, and then select the units you want to assign.
• To select units that have already been used in the model, click , choose Used in this model, and then select the units you want.
• To select units that you have created previously, either for the model you are working on or as a preference, click , choose the My Units category, and then select the units you want. For more information about creating units of measure, see Creating and deleting unit definitions.

• To have the software specify the appropriate units, click , and then choose Suggest units. The software determines the correct units and displays them in the Units box.

  Note: This option is available only if the software is able to determine the units from the equation.

4. When the units you want to assign are displayed in the Units box, click or move to another task and the units will be retained.

See Also