I am learning about non-linear dimensionality reduction (so far only older stuff like isomap and LLE). And I had a few questions:
Most implemented packages for isomap that I found (in R) simply mapped all my data to the manifold they "found". Is there a way to get the map itself (function mapping from input space to the manifold)? So that I would be able to learn the manifold on the training set and apply it to test sets?
What are the newer/better methods for non-linear dimensionality reduction?
How does non-linear reduction perform for small sample sizes (p >> n)?
Thanks a lot, PMW.
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