Page 675 - ExtendSim User Guide
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Analysis 649
Sensitivity analysis
• Enable,disable,anddeletesensitivitysettingsforaparticularparameterusingtheSensitivity Setup dialog.
When you enter sensitivity settings for a value, sensitivity analysis is enabled as long as the Enable sensitivity box is checked in the Sensitivity Setup dialog. If you uncheck the box, a dialog value’s sensitivity is temporarily disabled so that you don’t have to re-enter the number for subsequent analysis.
To remove sensitivity settings from a parameter (as compared to simply temporarily disabling the settings by turning off the parameter’s Enable sensitivity box), open the Sensitivity Setup dialog using any of the methods discussed on page 647, then click Delete.
☞ Editing a sensitized parameter in a block’s dialog disables the sensitivity settings for that block. When this happens, ExtendSim automatically unchecks the Enable sensitivity choice. ExtendSim assumes that if the value is edited, you want to use that new value, not the one that was entered in the Sensitivity Setup dialog. If you want to turn off sensitivity analysis for a parameter for the foreseeable future, open that item’s Sensitivity Setup dialog and click the Delete button. This will help prevent accidentally changing the value in a future run of the sim- ulation.
A parameter that has sensitivity settings has a frame inside of it. If sensitivity analysis is active for the parameter (that is, if the Enable sensitivity choice is checked), the frame is green. If the sensitivity analysis is inactive for the parameter or if it is turned off for the model as a whole, the frame is red.
The Edit > Open Sensitized Blocks command shows the dialogs of all blocks with sensitized parameters, regardless of whether or not sensitivity is enabled.
Reporting the results
In addition to MultiSim and Error Bar plotters, ExtendSim’s reporting and tracing features are useful when analyzing output after using sensitivity analysis. The Reporting features show final values and the Trace feature shows values at each step or event. For more information, refer to “Reports” on page 689 and “Model tracing” on page 726.
Multi-dimensional scenarios
Sensitivity can be enabled on more than one item at a time. For instance, you may want to vary the values of two Constant blocks and see the interaction between the two items. If you set the sensitivity for the parameters with the Starting at option, both values will increment at the same rate. For instance, if you have one parameter start at 5 and increment by 1, and the second parameter start at 100 and increment by 50, and the simulation is run seven times the value pairings will be:
Run #
0 1 2 3 4
Variable 1
5 6 7 8 9
Variable 2
How To

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