n class="comment">% initialize</span>
0012     iOrder = 4;
0013     f_min = 300;
0014     k_min = round(f_min/f_s * 2 * (size(X, 1)-1)) + 1;
0015 
0016     afHps = X;
0017     
0018     <span class="comment">% compute the HPS</span>
0019     <span class="keyword">for</span> j = 2:iOrder
0020         afHps = afHps .* [X(1:j:<span class="keyword">end</span>, :); zeros(size(X, 1)-size(X(1:j:<span class="keyword">end</span>,:), 1), size(X, 2))];
0021     <span class="keyword">end</span>
0022     
0023     <span