Principal Component Analysis – the original paperADRIAN FLOREAPAPERS WE LOVE – BUCHAREST CHAPTER – MEETUP #12DECEMBER 16 T H , 2016

Karl Pearson, 1901

K. Pearson, "On lines and planes of closest fit to systems of points in space",The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science, Sixth Series, 2, pp. 559-572 (1901)

(1857-1936)

Dimensionality reduction (Pearson’s words)

(1901)

Dimensionality reduction (115 years later)

(2016)

71291 points200 features2 principal components

https://projector.tensorflow.org

Dimensionality reduction

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• r << d• n observations• r uncorrelated features• retain most of the data variability

transform

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New data set

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PCA algorithm1. Normalize to zero-mean, unit-variance

2. Calculate the covariance matrix of the normalized data set

3. Find all eigenvalues of and arrange them in descending order

4. Choose r for the top r eigenvalues (and corresponding eigenvectors/principal components)

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PCA Pros & ConsPROS

• dimensionality reduction can help learning

• removes noise

• can deal with large data sets

CONS

• hard to interpret

• sample dependent

• linear (

Bibliography• A.A. Farag, S. Elhabian, "A Tutorial on Principal Component Analysis" (2009) - http://dai.fmph.uniba.sk/courses/ml/sl/PCA.pdf

• N. de Freitas, "CPSC 340 - Machine Learning and Data Mining Lectures", University of British Columbia (2012) - http://www.cs.ubc.ca/~nando/340-2012/lectures.php

• I. Georgescu, “Inteligență computațională“, Editura ASE (2015)

• I.T. Jolliffe, "Principal Component Analysis", 2nd ed., Springer (2002)

• J.N. Kutz, "Data-Driven Modeling & Scientific Computation. Methods for Complex Systems & Big Data", Oxford University Press (2013)

•J. N. Kutz, "Singular Value Decomposition" - http://courses.washington.edu/am301/page1/page15/video.html

• K. Pearson, "On lines and planes of closest to systems of points in space", Philos. Mag, Sixth Series, 2, pp. 559-572 (1901) - http://stat.smmu.edu.cn/history/pearson1901.pdf

• M.J. Zaki, W. Meira Jr., “Data Mining and Analysis. Fundamental Concepts and Algorithms”, Cambridge University Press (2014)