a (n,1) or a (1,n) vector</span>
0055 addRequired(ip, <span class="string">'t'</span>, @(t) (isnumeric(t) || isdatetime(t)) &amp;&amp; (size(t,1)==1 || size(t,2)==1))
0056 
0057 <span class="comment">% optional input arguments</span>
0058 addParameter(ip, <span class="string">'recession_length'</span>, 5, @isnumeric) <span class="comment">% length of decreasing</span>
0059 <span class="comment">% flow in days to be declared a recession</span>
0060 addParameter(ip, <span class="string">'n_start'</span>, 1, @