Explanation of conditions at Roboschool Half-Cheetah

Question

I have some questions regarding the demigod.

• I see that the viewing space for Half-Cheetah is 26. Can someone tell me what the value is for? - I only counted 18. (also some of the values ​​seem to remain 0 for all timestamps)

• There is the following comment in half_cheetah.xml in roboschool / mujoco_assets:

  Model Cheetah

The state of space is filled with joints in the order in which they are defined in this file. Drives also work on connections.

State-Space (name/joint/parameter):
    - rootx     slider      position (m)
    - rootz     slider      position (m)
    - rooty     hinge       angle (rad)
    - bthigh    hinge       angle (rad)
    - bshin     hinge       angle (rad)
    - bfoot     hinge       angle (rad)
    - fthigh    hinge       angle (rad)
    - fshin     hinge       angle (rad)
    - ffoot     hinge       angle (rad)
    - rootx     slider      velocity (m/s)
    - rootz     slider      velocity (m/s)
    - rooty     hinge       angular velocity (rad/s)
    - bthigh    hinge       angular velocity (rad/s)
    - bshin     hinge       angular velocity (rad/s)
    - bfoot     hinge       angular velocity (rad/s)
    - fthigh    hinge       angular velocity (rad/s)
    - fshin     hinge       angular velocity (rad/s)
    - ffoot     hinge       angular velocity (rad/s)


Actuators (name/actuator/parameter):
    - bthigh    hinge       torque (N m)
    - bshin     hinge       torque (N m)
    - bfoot     hinge       torque (N m)
    - fthigh    hinge       torque (N m)
    - fshin     hinge       torque (N m)
    - ffoot     hinge       torque (N m)

Could you confirm to me if the order presented here coincides with the order of their appearance in the observation matrix? If so, should the values ​​always be taken into account?

Thank.