t-SNE perplexity — what does it control?
mediumAnswer
- Perplexity ≈ effective number of neighbors each point 'considers' when building the conditional similarity distribution.
- Typical range: 5-50.
- Low perplexity → local, may fragment groups.
- High → global, may merge distinct clusters.
- Rule of thumb: try 5, 30, 50 and inspect.
- Don't over-tune to make plots look better — the map should be robust across a range.
Check yourself — multiple choice
- Random
- Effective #neighbors per point; low → local/fragmented; high → global/merged; try 5, 30, 50 — plot should be robust across range
- Same as k
- Not real
Perplexity: effective neighbor count; typical 5-50; try multiple values.
#dimensionality-reduction#visualization
Practise Unsupervised Learning
214 interview questions in this topic.