MATLAB Plotting Transfer Functions Using Matlab

[mpm]

I am using a bode plot program using Matlab to try and plot transfer functions.

Here is the program I have:
http://www.swarthmore.edu/NatSci/echeeve1/Ref/Bode/BodePlotGui.html

Everytime I try and type in the command that it says to use, it gives me a tf is an unknown variable.

Does anyone know how I can get this to work?

 

[mpm]

I figured out how to get the zeros, poles, and gain by using this:

num = [2 3];
den = [1 4 0 5];
[z,p,k] = tf2zp(num,den)

But I can't figure out how to plot this to find the frequency response and bandwidth.

Note: I am just trying to find alternatives since I can't get this other program to work. Anything that works I will use.