QXcbConnection: Could not connect to display

[TCIII]

I am running Raspbian Stretch and ROS Kinetic on a Rpi 3B+.

I have successfully built the ROS Desktop option, but I am getting the following message when using the roslaunch rplidar_ros view_rplidar.launch command string"

QXcbConnection: Could not connect to display
[rviz-3] process has died [pid 7994, exit code -6, cmd /opt/ros/kinetic/lib/rviz/rviz -d /home/pi/rplidar_ws/src/rviz/rplidar.rviz __name:=rviz __log:=/home/pi/.ros/log/bf3bc964-d237-11e9-a538-b827ebcb393e/rviz-3.log].
log file: /home/pi/.ros/log/bf3bc964-d237-11e9-a538-b827ebcb393e/rviz-3*.log

Viewing the RPLidar output using the Test application commands works fine:

roslaunch rplidar_ros rplidar.launch
rosrun rplidar_ros rplidarNodeClient

Since I am new to ROS programming, can anyone tell me why I am getting the error with the rplidar.rviz function?

Regards,
TCIII