• Logistic PCA
    • allow for dealing with binary and categorical (discrete) input features
  • Sparse PCA
    • overcome a PCA weakness that PCs are usually linear combinations of all the input features by using linear combinations of just a few input variables
  • Nonlinear PCAs
  • Robust PCAs
    • overcome the PCA weakness that PCA is sensitive to outliers in the data that cause large errors, e.g., weighted PCA.
  • Probabilistic PCA
    • a stochastic PCA variant (generative model) that explains the PCA process from a data generation perspective