MATLAB grader error when running code

I'm using MATLAB grader for an assignment in my class, and this assignment has worked before, but now is not. The code that's being run is this:

num1 = [1]; %numerator of filter
den1 = [1 1]; %denominator of filter
filter1 = tf(num1, den1)  %Filter transfer function object

And the error:

Undefined function 'tf' for input arguments of type 'double'.

Error in solution (line 3)

filter1 = tf(num1, den1) %Filter transfer function object

[KALYAN ACHARJYA]

When I checked, no error

filter1 =

    1
  -----
  s + 1
 
Continuous-time transfer function.

[Diane Peters]

Wow, that's weird. My student showed me the error and then I went into learner preview and saw it myself.

Answer 1

[Cris LaPierre]

The likely problem is that your course is running only using base MATLAB, but it needs to have the Control System toolbox in order to run the tf function.

For courses being offered on grader.mathworks.com, you need to specifically add the products (toolboxes) you want your students to have access to to your course. See this page in the documentation to see how to add the Control System toolbox to your coures.

[Diane Peters]

That was it, thank you very much.