help me for work with Octave

                                                                 This error
message occurs when I want to use software to solve control problems.
Please help fix these bugs


>> G=tf(num_G,den_G);
error: 'tf' undefined near line 1, column 1

The 'tf' function belongs to the control package from Octave Forge which
you have installed but not loaded.  To load the package, run 'pkg load
control' from the Octave prompt.

Please read <https://www.octave.org/missing.html> to learn how you can
contribute missing functionality.
>>