error in roslaunch nav2d_tutorials tutorial1.launch

edit

hi ! when i run : roslaunch nav2d_tutorials tutorial1.launch

i have this error :

ERROR: cannot launch node of type [stage_ros/stageros]: can't locate node [stageros] in package [stage_ros] ERROR: cannot launch node of type [nav2d_operator/operator]: can't locate node [operator] in package [nav2d_operator] ERROR: cannot launch node of type [joy/joy_node]: can't locate node [joy_node] in package [joy] ERROR: cannot launch node of type [nav2d_remote/remote_joy]: can't locate node [remote_joy] in package [nav2d_remote] ERROR: cannot launch node of type [rviz/rviz]: can't locate node [rviz] in package [rviz]

refrence : link text

how can i fix that error ????