Unsupervised Deep Learning¶
Traditional Autoencoder¶
Feature learning, dimensionality reduction, anomaly detection
flowchart LR
x1["x"] -->
|Encoder| z["z"] -->
|Decoder| x2["x̂"]
- Usually \(\vert z \vert < \vert x \vert\), to find useful small subset of features
- Sometimes encoder and decoder share weights
- Use encoder to initialize a supervised model
Error function will be \(u_i = x_i - \hat x_i\)
Variational Autoencoder¶
- Bayesian
- Useful to generate new data
GAN¶
Generative Adversarial Networks
flowchart LR
n[/Noise/] ---> g[Generator] --> d
rd[Real Data] -->
d[Discriminator] -->
rf{Real/Fake} -.->
|Backpropagation| d & g