  Accelerated destructive degradation tests (ADDT) are often used to collect
necessary data for assessing the long-term properties of polymeric materials.
Based on the data, a thermal index (TI) is estimated. The TI can be useful for
material rating and comparisons. The R package ADDT provides the
functionalities of performing the traditional method based on the least-squares
method, the parametric method based on maximum likelihood estimation, and the
semiparametric method based on spline methods for analyzing ADDT data, and then
estimating the TI for polymeric materials. In this chapter, we provide a
detailed introduction to the ADDT package. We provide a step-by-step
illustration for the use of functions in the package. Publicly available
datasets are used for illustrations.
