procedure bode(num[1],den[1],f[1],out L[1],out fi[1])
  k=cols(f);
  fi0=0;
  for (i=1,k) 
  begin
    c=complex(0,f[i]);
    cn=polyval(num,c); c=polyval(den,c);
    if abs(c)>0 then c=cn/c;
    a=abs(c);
    if a>0 then L[i]=20*ln(a)/ln(10) else L[i]=-100;
    fi[i]=arg(c)*180/pi;
    while abs(fi[i]-fi0)>180 do
      if (fi[i]-fi0)>180 then fi[i]=fi[i]-360 else fi[i]=fi[i]+360;
    fi0=fi[i];
  end;
end;