hello,
what happened when I type roscd,
it showed commnad not found?
I type ros and tab it show below,
and I find that roscd is missing...
How I fixed that?

sam@sam-desktop:~$ ros
rosbag           rosgraph         rosnode          rossrv
rosboost-cfg     roslaunch        rospack          rosstack
rosclean         roslaunch-deps   rosparam         rostest
rosconfig        roslaunch-logs   rosplay          rostopic
roscore          roslocate        rosrebag         rosversion
roscreate-pkg    rosmake          rosrecord        roswtf
roscreate-stack  rosmaster        rosrun
rosdep           rosmsg           rosservice
sam@sam-desktop:~$ roscd
roscd: command not found
sam@sam-desktop:~$