Creating a project

1. Create a new project by clicking the New button on the toolbar or by selecting File | New from the Menu bar.
2. Make sure that the Modeling layout is visible by clicking the Modelling button on the toolbar.

Adding algebraic expressions

The algebraic expressions of the model are implemented by creating Expression blocks. There are several ways of creating Expression blocks:

• In the Interaction matrix of the Matrix window
• In the Blocks window
• When entering expressions for other objects.
• In the Graph window.

In this lesson we will explore the first three ways. The Graph window will be covered in a later tutorial.

Creating Income using the Matrix window

1. Make sure that the Matrix window is opened by selecting Window | Matrix from the Menu bar.
2. Right-click the first diagonal element in the Interaction matrix. Select Expression from the pop-up menu.
3. Double-click the Expression, or right-click it and select Edit from the pop-up menu.
4. Make sure that the Properties tab is selected, and enter “Income” in the Name field.
5. Select the Values tab. In the Value column, write the expression “Sales + Fees” on the Expression row and press Enter. A window will appear as two unknown objects are referred to in the expression. These are both time-dependent input values, select “Lookup Table” from the Type drop-down list for both Sales and Fees. Click Ok.
6. Close the edit window by clicking Ok

Creating Profit from the Blocks window

1. Make sure that the Blocks window is visible by selecting Window | Blocks from the Menu bar. The window should list the three Blocks that you have already created: Income, Sales and Fees.
2. Either select “Expression” from the Type drop-down list and click the New button on the title bar, or right-click the window and select Create | Expression from the pop-up menu.
3. In the table, click the Name field for the newly created Expression and write “Profit”.
4. Next, click the Value field for the Expression and write “Income - Expenses”. Like before, Ecolego will discover unknown objects when you click Enter. The unknown object is “Expenses”; select “Expression” from the Type drop-down list. Click Ok to close the window.

1. You should now see a new Expression in the list of blocks named “Expenses”. Enter “Salary + Tax + Rent” in the Value field, where

• Salary is a Parameter
• Tax is an Expression
• Rent is a Parameter

Using the Expression editing tool

1. Instead of writing the equation for the Tax Expression directly, right click the Tax block in the table and select Edit from the pop-up menu.
2. Make sure that the Values tab is selected.

1. Click the Equation field of the table. The Expression editing tool will appear to assist you when writing the expression. As you see, there is a list of all blocks of your model. Double-click Income to add it to the expression. Click the asterix (’*’) on the key-pad, and then write “TaxRate” so that the full expression becomes “Income * TaxRate”. When you press Enter and the “Unknown values” window appears, select “Parameter” for TaxRate.
2. Click Ok to close the windows.
   

Next

• Defining inputs (3/5)

Previous

• Creating a simple model

References

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