1X2 vector of the module and argument of the poles and the zeros of the filters

string : 'a' for amplitude, 'gd' for group delay; default case for amplitude and group delay.

frequencies where the filter specifications are given

weighting functions for the amplitude and the group delay

weighting (with 1-lambda) of the costs ('a' and 'gd' for getting the global cost.

desired amplitude and group delay

criterium and gradient values