I am confused between what types of problems these three models capture, and their applications:
- Latent Dirichlet Allocation (LDA)
- Dirichlet Processes and Pitman-Yor processes
- Hierarchical Dirichlet Process (HDP) & Hierarhical Pitman-Yor Processes
More than formal definitions (which I can find on Wikipedia), I am looking for the intuition behind each of them ( how they build on each other).
Perhaps, more specifically:
- Is the difference between LDA and HDP that LDA is parameteric (i.e. I need to pre-specify the number of topics) whereas HDP is non-parametric? (and therefore I don't need to know how many topics I have)
- What is the difference between a Dirichlet Processes and Pitman-Yor Processes?
- What is the difference between a non-parametric process (e.g. DP) and a hierarhical non-parametric process (e.g. HDP)?