Fig. 5From: Exploiting temporal and nonstationary features in breathing sound analysis for multiple obstructive sleep apnea severity classificationAveraged four NMF activation matrices based on the final nonstationary subset features. Dimension-reduced nonstationary features, the NMF activation matrices show different distributions of corresponding magnitudes for each dimension-reduced cycle frequency α and spectral f index pair: a normal b mild OSA, c moderate OSA, and d severe OSABack to article page