2] = size(Y);
0066 <span class="keyword">if</span> (D1~=D2),  error(<span class="string">'X and Y must have the same number of columns.'</span>);  <span class="keyword">end</span>;
0067 <span class="keyword">if</span> (~isreal(X) || ~isreal(Y) || ~isa(X,<span class="string">'double'</span>) || ~isa(Y,<span class="string">'double'</span>))
0068     error(<span class="string">'Input matrices must be real-valued matrices of type double.'</span>);
0069 <span class="keyword">end</span>
0070     
0071 <span class