Home → Techniques and Tips → @RISK Simulation: Graphical Results → Combining Inputs in a Sensitivity Tornado
Applies to: @RISK 5.x–7.x
How can I aggregate multiple inputs in the tornado graph, so that I see the output's sensitivity to the combination instead of sensitivities to the individual inputs?
I might be combining countries in a region, or I might want an NPV instead of individual cash flows, or ...
The RiskMakeInput( ) functions lets you do exactly this. If you already have a formula in your workbook that computes the aggregate you're interested in, just wrap it in a RiskMakeInput( ), like this:
=RiskMakeInput(
formula, RiskName("
name to appear in tornado") )
As an alternative, you could just create that formula in an empty cell.
RiskMakeInput( ) tells @RISK that its contents should be treated as an @RISK input distribution for purposes of sensitivity analysis, and RiskMakeInput( )'s precedents should be ignored in sensitivity analysis. Implications:
Precedent tracing stops with the RiskMakeInput( ), effectively. @RISK looks at the cells that the formula in RiskMakeInput( ) refers to, and all precedents of those cells. Any distributions that are direct or indirect precedents of any RiskMakeInput( ) function are excluded from all sensitivity calculations for all outputs. Even a RiskMakeInput( ) among those precedents is excluded from sensitivities.
The RiskMakeInput need not be a precedent of the output. For example, suppose you have =RiskMakeInput(A1+A2) in cell A3, and an @RISK output in cell A4. If the formula in A4 refers to A1 or A2 or to any of their precedents, then @RISK will treat the RiskMakeInput( ) in A3 as a precedent of the output in A4, even if the formula in A4 doesn't refer to A3 directly or indirectly. In this respect, @RISK treats RiskMakeInput( ) as a precedent even though Excel may not. Another way to look at it is that @RISK treats a RiskMakeInput( ) function as a precedent of an output if the two have any precedents in common.
The RiskMakeInput( ) affects all sensitivity measures, including all graphs and the RiskSensitivity( ) and RiskSensitivityStatChange( ) worksheet functions.
For an example, in @RISK 6 or 7 click Help » Example Spreadsheets » Statistics/Probability » Using RiskMakeInput Function. In @RISK 5, click Help » Example Spreadsheets » RiskMakeInput.xls.
See also: Excluding an Input from the Sensitivity Tornado
Last edited: 2015-06-21