s="comment">%       to April or [5:9] for May to September</span>
0012 <span class="comment">%   OPTIONAL</span>
0013 <span class="comment">%   option: option to delete values outside subperiod ('delete') or assign</span>
0014 <span class="comment">%       NaN to values outside subperiod ('nan')</span>
0015 <span class="comment">%</span>
0016 <span class="comment">%   OUTPUT</span>
0017 <span class="comment">%   X_sub: subperiod time series</span>
0018 <span class="comment">%   t_sub: subperiod time</span>
