How to write the expression in matlab

How to write the expression : (2-s^500-3s^700)/(1-11s^400-20s^700)

Answer 1

[Star Strider]

First, add the required multiplicaiton operators, then:

s = tf('s');
H = (2-s^500-3*s^700)/(1-11*s^400-20*s^700)

H =

      3 s^700 + s^500 - 2
    -----------------------
    20 s^700 + 11 s^400 - 1

Continuous-time transfer function.

This requires the Control System Toolbox, or a related Toolbox.

[phoenix]

Thank you strider. What is the difference between the command s=tf('s') and s=tf('z')? Can the same thing be written as:(2-z^-500-3*z^-700)/(1-11*z^-400-20*z^-700)?

[Star Strider]

The difference is that ideally you specify a sampling interval (or inter-sample interval) when you specify a discrete transfer function.

It otherwise works essentially the same:

z = tf('z');
H = (2-z^-500-3*z^-700)/(1-11*z^-400-20*z^-700)

H =

     2 z^2300 - z^1800 - 3 z^1600
    ------------------------------
    z^2300 - 11 z^1900 - 20 z^1600

Sample time: unspecified
Discrete-time transfer function.