_results: whether to plot results, default = false

   OUTPUT
   flow_section: n-by-2 array where n is the number of recession segments;
       columns are the indices into the flow array of the start and end of
       the recession segments
   error_flag: 0 (no error), 1 (warning), 2 (error in data check), 3
       (error in signature calculation)
   error_str: string contraining error description
   fig_handles: figure handles to manipulate figures (empty if plotting is
       not requested)

   EXAMPLE
 