d">return</span>
0017 <span class="keyword">end</span>
0018 
0019 n = 0;
0020 ts = 0;
0021 <span class="keyword">if</span>(isempty(filename))
0022    [fname, pathname] = uigetfile(<span class="string">'*.plx'</span>, <span class="string">'Select a plx file'</span>);
0023     filename = strcat(pathname, fname);
0024 <span class="keyword">end</span>
0025 
0026 fid = fopen(filename, <span class="string">'r'</span>);
0027 <span class="keyword">if</span>(fid == -1)
0028     disp(<span class="string">'cannot open