HomeTechniques and Tips@RISK Distribution FittingConstraining Time Series to Return Positive Results

4.18. Constraining Time Series to Return Positive Results

Applies to: @RISK 6.x/7.x Industrial Edition

I'm using Time Series in @RISK 6. I want to ensure that the projected results are greater than zero. I tried using RiskTruncate, but the manual says that RiskTruncate and RiskShift aren't effective with time series. Is there a way to do what I want?

Yes, assuming that the original data are greater than zero.

In the fit dialog, select Function and then Logarithmic. The data will be transformed according to that function. After the fit, the projected data are de-transformed. De-transforming a logarithm means exponentiating, and the range of the exponential function is all positive numbers.

You'll want to experiment a bit and make sure that doesn't have any undesirable side effects with your particular data set.

Last edited: 2015-06-19

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