Principal Coordinates Analysis (PCoA)

- PCA on arbitrary distance matrix
- Used in omics
- https://claude.ai/share/fd959db3-7967-4e15-b9e5-3e9d052100f9
- https://stats.stackexchange.com/questions/14002/whats-the-difference-between-principal-component-analysis-and-multidimensional
- MDS is already in sklearn, maybe no need to implement