Figure 2.

Illustrates effectiveness of proposed ℓ₁-sparsity filtering approach

a Original ECG signal taken from MIT/BIH arrhythmia database record 208 containing narrow- and wide-QRS complexes and baseline wander

b Estimated sparse coefficients $\tilde{\mathit{\alpha }}$ using predefined OHD matrix and regularisation parameter λ = 0.3

c Detail signal (or QRS feature signal) obtained for 3600 × 1 coefficients corresponding to 3600 × 3600 impulse dictionary

d Approximation signal obtained for 80 × 1 DCT coefficients vector corresponding to DCT dictionary