ed).
 
  The full format of the function is:
  [x,f,info] = lbfgsb( fcn, l, u, opts )
    where the output 'f' has the value of the function f at the final iterate
    and 'info' is a structure with useful information
        (self-explanatory, except for info.err. The first column of info.err
         is the history of the function values f, and the second column
         is the history of norm( gradient, Inf ).  )
 
    The 'opts' structure allows you to pass further options.
    Possible field name value