Defining the fox population as a function of time

• Double click ‘Foxes at start’ node.

Expected: Object window should appear.

• In the Description field type ‘The fox population at the start of each time period’.

Expression Assist

Use the Expression assist to set the definition:= Dynamic(6,Foxes_at_end[Time-1]*(1+Fox_birth_rate))

• Select definition
• Enter 'D

Expected: the expression assist offers possible entries starting with D

• Enter 'y'

Expected: The list truncates to only include those starting with DY

• Use the down arrow to select Dynamic and tab to select it

Expected: Dynamic( in the definition

• Enter 6,

Expected, Expressions Assist moves to the next parameter.

• Continue using the expression assist to enter the definition as depicted.

• Double click ‘Foxes at end’.

Expected: Object window should appear.

• . Type ‘The fox population at the end of each time period’ in the Description field.

• Click the Definition field. Click ‘Inputs’ popup menu button, select ‘Foxes_at_start’.

• ‘Foxes_at_start’ should appear on the Definition field. Click on the check button to accept your entry. Click on the diagram button.

• With the Foxes at end node selected, click on the result button. Result window should appear.

See Also

• Tutorial: Dynamic system model
• Creating the Foxes and Hares model (based on chapter 7 of tutorial)