Custom Relationship

In the Fit Life by X launch window, you can specify a custom transformation to model the relationship between a lifetime event and an accelerating factor. Enter comma delimited values into the entry fields for the location (μ) and scale (σ) parameters. For a data table that contains a column named Temp, an example entry for μ could be “1, log(:Temp), log(:Temp)^2”, and an entry for σ could be “1, log(:Temp)”, where 1 indicates that an intercept is included in the model. Select the Use Exponential Link check box to ensure that the sigma parameter is positive.

Figure 4.18 Custom Relationship Specification in Fit Life by X Launch Window 

After selecting OK, location and scale transformations are created and included at the bottom of the Estimates report section.

Figure 4.19 Weibull Estimates and Formulas for Custom Relationship 

For an example of how to use a custom transformation, see Additional Example of the Fit Life by X Platform. Analysis proceeds similarly to the Example of the Fit Life by X Platform, where the Arrhenius Celsius Relationship was specified.