For most simulations it is easiest to simulate directly from the Toolbar. There are some settings that are not available from the Toolbar (for example loading changes files) and for these you will need to use the Simulation Control dialog discussed later in this chapter. Once you have set something in the Simulation Control dialog it will remain set so you can simulate from the Toolbar and have additional options included. For example, if you specify a changes file in the Simulation Control dialog each time you simulate that changes file will be used.
NOTE Vensim PLE and PLE Plus only support simulation from the Toolbar, and not all of the options described below are available.
To simulate the current model with the settings last used for a simulation (or the default settings if this is the first simulation) click on the Simulate 
button or type Crtl+R. To enter SyntheSim mode click on the SyntheSim 
button. The name appearing in the toolbar will be used for the simulation. If you want to change the integration method, data files to be used or make temporary changes to Constants and Lookups click on the Set up a Simulation 
button. The top Toolbar will change appearance:
If you are working in the Sketch Editor, the sketch view will also change appearance. All Constants and Lookups in the current view will be highlighted. You can make temporary (for this simulation run only) changes to their values by clicking on them.
| • Clicking on an unsubscripted Constant will bring up the Constant's value in an editing box. Type in a new value and press the Enter key to change it. |
| • | Clicking on a subscripted Constant will bring up the Constant Changes dialog discussed under "Changing Constant and Lookup Values" later in this chapter. You can use this to change any element of the subscripted constant. |
| • | Clicking on an unsubscripted Lookup will open the Graph Lookup Editor, allowing you to change values. |
| • | Clicking on a subscripted Lookup will bring up the Lookup Changes dialog allowing you to select which element you want to change. |
In addition to regular variables, any Input Objects that are attached to model Constants will be activated. You can change the values of the corresponding Constants by dragging the slider or typing in a new value. Note that it is a good idea to put labels near to these sliders to make it clear which variables they are changing.
While in Simulation Setup model you can move from view to view and change any Constants and Lookups you wish. You cannot, however, make any changes to views.
You can select the Integration method to be used in the simulation by clicking or shift clicking on the left most button. If will cycle through Euler for Euler integration, RK4 for 4th order Runge Kutta, Diff for difference equations, RK2F for 2nd order Runge Kutta with fixed step size, RK2 for 2nd order Runge Kutta and RK4F for 4th order Runge Kutta with fixed step size (then start again). The different integration techniques are discussed further below. Use Shift+Click to move backward through the list.
If you have a model that uses data variables you will need to include the name of the driving datasets in the first edit box. You can select a dataset by clicking on the : button to the right. The dataset you select will replace the current selection in the editing box, or be added to the contents of the editing box if nothing is selected. If you only want to use one dataset be sure to highlight the old one before selecting a new one.
If you want to get a list of all model Constants and Lookups, you can click on the Constant and Lookup 
buttons. These bring up the Constant Changes Dialog and Lookup Changes Dialog for all the Constants and Lookups in the Model.
You can open the Simulation Control Dialog by clicking on the 
button. Any changes you have made on-screen will be retained. You will need to start the simulation from this dialog as described below.
Once you have made all your changes you can simulate the model by clicking on the Simulate 
button. The simulation will be given the name appearing in Runname editing box on the Toolbar. In addition to a regular simulation you can also start a gaming simulation 
, a sensitivity simulation 
, an optimization 
or a Reality Check run 
. You can also cancel the simulation by clicking on the Stop 
button. Gaming is discussed below. Sensitivity and Optimization are discussed in Chapter 9. Reality Check simulations are discussed in Chapter 14 of the User's Guide.
When you set up a simulation from the Toolbar with a sketch open the Lock tool is automatically selected into the sketch and any Output Objects are filled. After you simulate the content of all output objects is renewed automatically ensuring that they are consistent with the latest simulation.
