Receiving error "Unrecognized function or variable 'tf'" even though I have the Signal Processing Toolbox installed.

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Matthew Crain
Matthew Crain 2021-6-6
评论： Brian Mcnulty 2022-4-18
I am trying to produce a bode plot using the tf function. My code is as follows:
num = [10000000000000000000000000000 7000000000000000000000000000000];
den = [1 7540690 21324854073600 26807731666619904000 12647107451415440994336768 10730685839764156310146252800];
G = tf(num, den)
bode(G),grid;
The error is in line 4. I am receiving the error message despite having the Signal Processing Toolbox installed. When I type "ver" into the command window I get this:
MATLAB Version: 9.10.0.1669831 (R2021a) Update 2
Operating System: Microsoft Windows 10 Home Version 10.0 (Build 19042)
Java Version: Java 1.8.0_202-b08 with Oracle Corporation Java HotSpot(TM) 64-Bit Server VM mixed mode
-----------------------------------------------------------------------------------------------------
MATLAB Version 9.10 (R2021a)
Signal Processing Toolbox Version 8.6 (R2021a)
I am new to MATLAB so I would appreciate any pointers. Thank you.
  2 个评论
Matthew Crain
Matthew Crain 2021-6-6
Nevermind! I found that I needed the Control Systems Toolbox add-on. Apparently the tf function is not a part of the Signals Processing Toolbox. The more you know!
Brian Mcnulty
Brian Mcnulty 2022-4-18
the 'tf' command is not recognized and the command window provides a reccomendation instead.
I have all the correct toolboxes installed, however, the error persists.
What can I do to alleviate this issue. Any suggestions would be greatly appreciated. Thank you in advance.

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回答（1 个）

Steven Lord
Steven Lord 2021-6-6
Ran in:
which -all tf
/MATLAB/toolbox/control/ctrlmodels/@tf/tf.m % tf constructor /MATLAB/toolbox/mpc/mpc/@mpc/tf.m % Shadowed mpc method /MATLAB/toolbox/control/ctrlmodels/@DynamicSystem/tf.m % Shadowed DynamicSystem method /MATLAB/toolbox/ident/ident/@idParametric/tf.m % Shadowed idParametric method /MATLAB/toolbox/shared/controllib/engine/@StaticModel/tf.m % Shadowed StaticModel method
There are several functions named tf in various MathWorks products, but most of them are intended for use in converting some sort of other object into a tf object. As you have learned the tf function in Control System Toolbox (the first on that list) is what you should use for creating a tf object from raw numeric data.

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