Running Simulations

Figure 9. The Control Panel buttons can be used to control the running of the simulation. From left to right, the buttons are "Reset", "Stop", "Step", "Go" and "Go For...". The number in the pull-down menu indicates the number of time intervals the simulation will run when "Go For..." is chosen. The number on the far right of the control panel indicates the current time in the simulation.

Figure 10. Speed Control. The up and down slider at the right side of the menu bar controls the speed of the simulation. In the figure, the slider is pictured at its highest (and fastest) value.

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Once you have set up a simulation, you can use the icons on the Control Panel (Figure 9) to see how the population size and age distribution change through time. Use the slider to the right of the control panel to control the speed of the simulation (Figure 10).

Go


To start the simulation running, click the ìGoî or "Play" button on the control panel. The simulation will continue running and the display windows will continue updating until you stop the simulation using the Stop button.

The ìGoî button is inactive except when the simulation is stopped, and will appear ìgrayed outî whenever the simulation is running.

Go For...

To run a simulation for a specified number of time intervals, click the ìGo For...î or "Play For..." button on the Control Panel. The simulation will run for the number of time intervals specified in the text box to the right of the button, and then stop automatically. You may specify the number of time intervals either by clicking in the text box and typing in a number, or by selecting a number from the pull-down menu that can be accessed using the down arrow to the right of the text box.

The ìGo For...î button is inactive except when the simulation is stopped, and will appear ìgrayed outî whenever the simulation is running.

Step


To run the simulation for only one time interval, click the ìStepî button on the Control Panel. The simulation will update all the display windows for only one time interval, then the simulation will stop. You can continue the run of the simulation from this point by clicking on the Go button, or you can continue to click the Step button as many times as you want. Each time it will update the simulation for one time interval.

The ìStepî command is inactive when the simulation is running, and will appear "grayed out.".

Stop


Whenever you want the simulation to stop running, click the Stop button on the Control Panel. This only stops the simulation; it doesnít quit the program, or end the problem you are working on, so donít worry. You can stop and start the simulation as often as you like.

The ìStopî command is inactive and will appear ìgrayed outî whenever the simulation is stopped.
Reset


After you start JAVA Demography, but before you have run the simulation by selecting ìGoî or ìStepî, you can set the ìinitial stateî for the run of the simulation. At any time you are running the simulation, you may want to return to this ìinitial stateî.

The ìResetî button on the Control Panel will set the population size and age distribution back to their initial values. It does not, however, change the fertility or mortality settings.

After choosing ìResetî a window will appear, asking you whether you want to save the current state, before returning to the ìinitial stateî. If you click ìSaveî, you will be setting a mark (see the Mark menu), and you will be asked to give it a name.

Current Time


The number on the far right of the Control Panel indicates the "current time interval" for the simulation.