Model and Data

3.1. Data Dataset consists of 98 ship engines that could be categorized with five types of engines. Therefore, our hierarchical model has a 1-5-98 structure; 1 engine archetype, 5 engine types, and 98 ship types. The numbers of ships in the five categories are also different as in section 2.1. Fig. 1 shows the age, type of engine, and ship of existing data. As can be seen from the figure, the amount of data for each category is highly unbalanced. Moreover, the similarity between data under the same category could be inferred; for example, data with the same type of engine display a similar age period.