matlb R7,and The instruction ( thd(x)) ?

I have matlab R7 , But when used instruction thd(x) in M file get this message?

??? Undefined command/function 'thd'.

Answer 1

[Jan]

Which Matlab 7 version are you talking of?

Do you have the signal processing toolbox installed and licensed?

[Mary Jon]

 I have not the signal processing toolbox installed and licensed

Answer 2

[Wayne King]

To follow up on Jan's answer, thd() was introduced in R2013b, so you would have to have the latest release of MATLAB -- 8.2.0.701 (R2013b) AND the Signal Processing Toolbox to use thd()

[Mary Jon]

Mr.King thd() not introduced in R2013a only in R2013b?

[Wayne King]

That is correct, thd() was introduced in R2013b in the Signal Processing Toolbox.