For what it's worth, the best PCA tutorial I've seen online is this blog post, which uses plots to describe the technique: http://stats.stackexchange.com/a/270

For what it's worth, the best PCA tutorial I've seen online is this blog post, which uses plots to describe the technique: http://stats.stackexchange.com/a/2700/2019 http://stats.stackexchange.com/a/2700/2019 PCA is nothing more than a "basis shift", or changing where the x and y axes are placed. This image-based tutorial makes understanding very intuitive.