function [bw,err] = bwcalc(db,omega,lfg_db)%       Determines the bandwidth of a system, either open- or %       closed-loop, by:%       1. evaluating the freq response for a number of frequencies%       2. finding the freq at which the magnitude is 3.0 db lower %          than the LFG%Inputs: db - vector of magnitudes (decibels) %        omega - vector of corresponding frequencies%        lfg_db - low-frequency gain (dB)%Outputs: bw - bandwidth, same scale as omega%         err - error flag%                1 -> mag at lowest freq was < lfg -3.0 (db)%                2 -> mag at all freq were > lfg -3.0%%%%%%%%%%%%%%%%%%% bwcalc.m %%%%%%%%%%%%%%%%%%%%%   Discrete-Time Control Problems using        %%       MATLAB and the Control System Toolbox   %%   by J.H. Chow, D.K. Frederick, & N.W. Chbat  %%         Brooks/Cole Publishing Company        %%                September 2002                 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%err = 0;bw = [];	    % evaluate freq response% get index of the frequency just after the% magnitude goes 3 db below the LFGkmax=length(db);flag=0;  % 1-> found a mag below lfg - 3.0for k=1:kmax  i=k;  if db(k) - lfg_db < -3.0    if k == 1      err=1; return    end    flag=1; break  endend% see if we got through all points without finding a crossingif i == kmax  if flag == 0    err=2; return  endend% we have a crossing if got here, so find bandwidth by interpolationslope=(db(i)-db(i-1))/(omega(i)-omega(i-1));delta=(lfg_db-3.0-db(i-1))/slope;bw=omega(i-1)+delta;return%%%%%%%%%