Figure 3

Results of removing collinear features in PPG + ECG feature set. Pairwise linear absolute Pearson’s \(|\rho _p|\) correlation matrix. (a) pre and (b) post removal of collinear features. Blank spaces represent non-significant (\(p > 0.05\)) or weak (\(|\rho _p| < 0.2\)) correlations. For clarity of labelling on the post-collinear feature set (b), every other label is presented on the y-axis with the remaining labels on the x-axis.