MATLAB: Output argument ‘f_assisted’ is not assigned on some execution paths! Help! I tried assigning f_assisted before the first if loop, after which it runs, but gives the same output for the whole simulation

matlab function

function f_assisted    = fcn(steering_torque, vehicle_speed)
if (vehicle_speed < 59)
    if vehicle_speed < 59 && (steering_torque == 0 & steering_torque < 2)
        f_assisted = steering_torque*1.2;
        flag =1
        if vehicle_speed < 59 && (steering_torque > 2.1 & steering_torque < 4)
            f_assisted = steering_torque*1.4;
            flag =1
            if vehicle_speed < 59 && steering_torque > 4
                f_assisted = steering_torque*1.6;
                flag=1
            end
        end
    end
elseif(vehicle_speed > 61)
    if vehicle_speed > 61 && (steering_torque == 0 & steering_torque < 2)
        f_assisted = steering_torque*0.4;
        flag=2
        if vehicle_speed > 61 && (steering_torque > 2.1 & steering_torque < 4)
            f_assisted = steering_torque*0.6;
            flag=2
            if vehicle_speed > 61 && steering_torque > 4
                f_assisted = steering_torque*0.8;
                flag=2
            end
        end
    end
elseif(vehicle_speed < 59)
    if vehicle_speed < 59 && (steering_torque == 0 & steering_torque > -2)
        f_assisted = steering_torque*1.2;
        flag=3
        if vehicle_speed < 59 && (steering_torque < -2.1 & steering_torque < -4)
            f_assisted = steering_torque*1.4;
            flag=3
            if vehicle_speed < 59 && steering_torque < -4
                f_assisted = steering_torque*1.6;
                flag=3
            end
        end
    end
elseif(vehicle_speed > 61)
    if vehicle_speed > 61 && (steering_torque == 0 & steering_torque > -2)
        f_assisted = steering_torque*0.4;
        flag=4
        if vehicle_speed > 61 && (steering_torque < -2.1 & steering_torque < -4)
            f_assisted = steering_torque*0.6;
            flag=4
            if vehicle_speed > 61 && steering_torque < -4
                f_assisted = steering_torque*0.8;
                flag=4
            end
        end
    end
else vehicle_speed = 60
    f_assisted = steering_torque*1.2;
     flag=5
end
end

Best Answer

The message is correct. Look at your code:
if (vehicle_speed < 59)
  if vehicle_speed < 59 && (steering_torque == 0 & steering_torque < 2)
It is impossible to reach the second "if" unless vehicle_speed < 59 from the first "if", so the test vehicle_speed < 59 on the second "if" is redundant, but will not otherwise cause a problem.
        f_assisted = steering_torque*1.2;
        flag =1
        if vehicle_speed < 59 && (steering_torque > 2.1 & steering_torque < 4)
Notice this is still inside the vehicle_speed < 59 && (steering_torque == 0 & steering_torque < 2), so you cannot get to this third "if" unless steering_torque is in the range 0 to less than 2, so (steering_torque > 2.1 & steering_torque < 4) can never be true at that point. The flip side of this is that the combination of conditions tested there vehicle_speed < 59 && (steering_torque > 2.1 & steering_torque < 4) is not otherwise tested, so if steering_torque > 2.1 then nothing will be assigned to f_assisted
You also have problems with 2 <= steering_torque <= 2.1 .
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