OpenCV Q&A Forum - RSS feedhttp://answers.opencv.org/questions/OpenCV answersenCopyright <a href="http://www.opencv.org">OpenCV foundation</a>, 2012-2018.Tue, 30 Jul 2013 05:40:12 -0500Fast PCA(principal component analysis)http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/I use PCA engine to compute pca but it is very slow.Is there a fast method to compute pca?Tue, 30 Jul 2013 00:39:58 -0500http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/Comment by mrgloom for <p>I use PCA engine to compute pca but it is very slow.Is there a fast method to compute pca?</p>
http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17786#post-id-17786If you need only few first principal components you can use iterative methods (I don't know if they fast enough) some info here http://scicomp.stackexchange.com/questions/3220/fastest-pca-algorithm-for-high-dimensional-dataTue, 30 Jul 2013 05:40:12 -0500http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17786#post-id-17786Comment by mrgloom for <p>I use PCA engine to compute pca but it is very slow.Is there a fast method to compute pca?</p>
http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17748#post-id-17748give more information about your task(size of the problem, number of principal components needed etc.)Tue, 30 Jul 2013 00:57:58 -0500http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17748#post-id-17748Comment by Guanta for <p>I use PCA engine to compute pca but it is very slow.Is there a fast method to compute pca?</p>
http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17775#post-id-17775OpenCV''s PCA is indeed not the fastest one (at least at the time I used it, maybe it changed in the meantime). Either use a different library for that or try to use SVD instead, you basically solve the same problem there, see http://math.stackexchange.com/questions/3869/what-is-the-intuitive-relationship-between-svd-and-pca how they are related.Tue, 30 Jul 2013 03:27:11 -0500http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17775#post-id-17775Comment by StevenPuttemans for <p>I use PCA engine to compute pca but it is very slow.Is there a fast method to compute pca?</p>
http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17762#post-id-17762PCA isn't supposed to run fast... It is an algorithm that has to calculate tons of covariance matrices, which takes time...Tue, 30 Jul 2013 02:11:29 -0500http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17762#post-id-17762Comment by Mostafa Sataki for <p>I use PCA engine to compute pca but it is very slow.Is there a fast method to compute pca?</p>
http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17752#post-id-17752features dimension = 4000 count = 20000.Tue, 30 Jul 2013 01:17:08 -0500http://answers.opencv.org/question/17745/fast-pcaprincipal-component-analysis/?comment=17752#post-id-17752