Undefined function 'tf' for input arguments of type 'double'.
显示 更早的评论
Hello everybody,
I have problem using the function "tf".
My code is as below:
p=bodeoptions;
p.grid='on';
p.Xlim={[1,500]};
p.XlimMode={'manual'};
num=[3.015,359.0,1.702e5];
den=[0.2758,120.9,55488.0,3.196e6,8.816e8];
sys=tf(num,den);
The error message is :
Undefined function 'tf' for input arguments of type 'double'.
I checked my toolbox and found the following information.
>> which tf
D:\Softwares\Study\Matlab2012b\toolbox\ident\ident\@idParametric\tf.m % idParametric method
>> which('tf','-all')
D:\Softwares\Study\Matlab2012b\toolbox\ident\ident\@idParametric\tf.m % idParametric method
D:\Softwares\Study\Matlab2012b\toolbox\shared\controllib\engine\@StaticModel\tf.m % StaticModel method
D:\Softwares\Study\Matlab2012b\toolbox\signal\signal\@dfilt\tf.m % dfilt method
>> ver
It seems my default "tf" function is not the controllib.tf. Is that the reason why it is wrong? How to make it right?
Thank you
回答（3 个）
Star Strider
2015-8-22
编辑：Star Strider
2015-8-22
I have the System Identification, Control, and Signal Processing Toolboxes, and the only tf function that comes up in the ‘Help’ documentation that has the syntax you are using is in the Control Systems Toolbox:
C:\Program Files\MATLAB\R2015a\toolbox\control\control\@tf\tf.m % tf constructor
C:\Program Files\MATLAB\R2015a\toolbox\control\control\@DynamicSystem\tf.m % DynamicSystem method
You have to have the Control Systems Toolbox to use it as you intend.
Zhou Xi
2015-8-22
0 个投票
2 个评论
John D'Errico
2015-8-22
编辑：John D'Errico
2015-8-22
No. You can only install toolboxes that are concurrent with your release. So you would need to upgrade your MATLAB release.
Star Strider
2015-8-22
John is correct. However, the tf function has been part of the Control Systems Toolbox since it was introduced in the 1990s, so the R2012 versions will have that function.
Zhou Xi
2015-8-24
1 个评论
Walter Roberson
2015-8-24
You might need to reinstall the Control System Toolbox.
Notice that the tf.m it found for controllib is for StaticModel objects only. Those do appear to be part of the Control Systems Toolbox, but they are certainly not the only tf.m that should be present for Control Systems.
类别
在 帮助中心 和 File Exchange 中查找有关 Control System Toolbox 的更多信息
2015-8-24
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
