Fig. 2

Overview of the basic principles of the principal component analysis. A Example data from two ECoG channels. Red and blue parts of the trace represent two types of fictional activity. B Plot visualizing how the data from the traces in A might be positioned in a two dimensional space. The colors of each point denotes which part of the trace it is a part of. Note that the coordinates of each point is fictional and given to maximize clarity. In this plot both the x- and y- coordinates are needed to determine the color of a point. C The gray vectors added to the plot shown in B to visualize where the principal component analysis might create new vectors, capturing as much of the information as possible. D Plot showing how the data from B would be positioned in the new coordinate system created by the principal component analysis. Please note that in this new coordinate system the y-coordinate would be enough to determine the color of a point, visualizing how the PCA increases the amount of information about the data contained in a dimension, without changing the positioning of the points in relation to each other.