2013/1/4 Andreas Mueller <[email protected]>: > On 01/04/2013 12:41 AM, Vlad Niculae wrote: >> Maybe my mind is not in its right place but how is that different from >> using the PCA transformer? >> > Not sure about my mind either but Lars talked about the SVD of X, not > the covariance matrix.
Indeed. In practical terms: when PCA subtracts the columnwise mean of X both in fit and in transform, it destroys the sparsity, so it's no good for sets of documents. See also http://metaoptimize.com/qa/questions/3340/difference-between-lsi-and-pca -- Lars Buitinck Scientific programmer, ILPS University of Amsterdam ------------------------------------------------------------------------------ Master HTML5, CSS3, ASP.NET, MVC, AJAX, Knockout.js, Web API and much more. Get web development skills now with LearnDevNow - 350+ hours of step-by-step video tutorials by Microsoft MVPs and experts. SALE $99.99 this month only -- learn more at: http://p.sf.net/sfu/learnmore_122812 _______________________________________________ Scikit-learn-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/scikit-learn-general
