Algorithm 3 The AS-TRCA method for SSVEP-BCI

Input:    Individual calibration data: $\mathit{X}\in {\mathbb{R}}^{N_c\times N_s \times { N}_t \times N_f}$    Test data: x $\in {\mathbb{R}}^{N_c\times N_s }$ Process:    Obtaining: ${\mathit{X}}_{e,1}\in {\mathbb{R}}^{N_c\times N_s{N}_f \times { N}_t }$    Initialization: old_$N_c$ ← $N_c$    While (1)        $Cs$← OCLS (${\mathit{X}}_{e,1}$)        $N_{c1}$ ← length  ($Cs$)         If   $N_{c1}$ == old_$N_c$                 break         else               old_$N_c$ ←$N_{c1}$   Obtaining: ${\widehat{\mathit{X}}}_{e,1}\in {\mathbb{R}}^{N_{c1}\times N_s{N}_f \times { N}_t }$ ${ N}_{sp}$ ← OSS (${\widehat{\mathit{X}}}_{e,1}$)    TRCA or other methods:       Feature extraction and Subspace feature fusion by (21)

Classification

Output: Classification result