Figure 2

The scatter plots of features for the two discriminative filters. (A) The training features extracted with the conventional CSP; (B) The training features extracted with TR-CSP; (C) The training features extracted with L1-SVD-CSP; (D) The testing features extracted with the conventional CSP; (E) The testing features extracted with TR-CSP; (F) The testing features extracted with L1-SVD-CSP. Red“+” represents the feature of left hand imagination, and green“o”denotes the feature of right hand imagination.