Project signal onto subspace

I have EEG recordings with me. I need to project a block of the signal onto a particular subspace (Ramanujam Periodic subspace) and calculate the energy of projection. How can I approach this in Matlab?

Code for Ramanujam sums and Ramanujam Periodic Subspace can be found here http://systems.caltech.edu/dsp/students/srikanth/Ramanujan/indexM.html

I couldn't understand the input for Cq (Ramanujam sums)