Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_setopt”.

  FT_SETOPT assigns a value to an configuration structure or to a cell-array
  with key-value pairs. It will overwrite the option if already present, or
  append the option if not present.
 
  Use as
    s = ft_setopt(s, key, val)
  where s is a structure or a cell array.
 
  See also FT_GETOPT, FT_CHECKOPT