Reconstruction from compressed representation

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Reconstruction from compressed representation
• PCA compression thousand into hundred dimensional features
• If there's a compressed algorithm, there should be uncompressed algorithm to give data compression back to its original value
• With this, we can uncompressed  the data reduction earlier, Ex hundred into thousand dimensional features(original_

• The graph above shows how we first make z1 projection line and give each example to be projected
• So how do we return the compressed back to original x?
• Left, original data, compressed then the right give the x approx
• Also called Reconstruction from the construct representation
• Quiz below , max retain should be equal to one. if more, than the data retain have over-variance over the original data.

SUMMARY
• These method shows us how we can convert the data reduction matrix z back to original x(or its original approximation)
• NEXT, mechanic how to use PCA well , how to choose k for reducing matrix z