Fig. 4.

Paired and unpaired data diagram. Three data types for feature selection: (a) pure-paired data type, which has pure case and control data; (b) mixed-paired data type, which has different mixing degree of mixture case and control data, (c) unpaired data type, which contains mixture case data without matched control data. It is noteworthy that the mixing degree is referred to the ratio between control part (blue) and case part (red) on one case sample, and vice versa on a control sample.