num=1;
den=[1,2,1];
bode(num,den);
hold on;
num=1;
den=[1,0.2,1];
bode(num,den);
num=1;
den=[1,0.02,1];
bode(num,den);

num=1;
den=[1,-0.02,1];
bode(num,den);
hold on;
num=25;
den=[1,0.1,25];
bode(num,den);
num=0.25;
den=[1,0.01,0.25];
bode(num,den);

num=100;
den=[1,0,100];
bode(num,den);

legend('1/(s^2+2s+1)','1/(s^2+0.2s+1)','1/(s^2+0.02s+1)', '1/(s^2-0.02s+1)', '1/(s^2/25+0.02s/5+1)', '1/(s^2/0.25+0.02s/0.5+1)', '1/(s^2/100+1)');