i can't use function tf() and bode()

 when i try a example: 
>> H = tf([1 0.1 7.5],[1 0.12 9 0 0]);
bode(H)
Undefined function 'tf' for input arguments of type 'double'.

as it appears on the error, I do not know what to fix desire to help people. thanks a lot

Answer 1

[Walter Roberson]

tf() is in the Control Systems Toolbox. That is not included in the Professional or Academic licenses, but is included in the Student Version license... but is not installed by default with the Student license.

[湘雅]

how to deal with it.....sad, thank you!

[Walter Roberson]

Use the Add-On Manager to search for Control Systems Toolbox. If it gives a simple option to install the toolbox, then go ahead and do that -- in that situation it would mean that you already have a license for the toolbox. But if it has a Buy button then you do not already have a license for the product, and would need to obtain a license.