What do you mean by "customized bagfile"? The Cartographer launch files actually just run rosbag play and Cartographer listens to the few topics it needs data from.

I mean our own Rosbag. How to run cartographer on my dataset? Please let me know the steps in detail. Thanks in advance.

I assume by "customized" you mean a bagfile you've collected on your robot? I can help but I'll need more information: do you want to run Cartographer in 2D or 3D? What sensors do you have? The more info you can post about your setup and sensors, the less assumptions I have to make.

Also, if you haven't done so already I highly suggest thoroughly reading the documentation. Try running the demos if you haven't already to get a feel for what the output looks like when everything is tuned and working properly.

https://code.google.com/archive/p/tu-darmstadt-ros-pkg/downloads these are some of the bag files that i am running. I have already run the demos.

I tried running a launch and config file over your bagfiles, but there's something odd about them as I keep getting a "frame_id cannot be empty" error.

Try those launch/config files for yourself (remember to update the filepath in the launch file) and if you get the same error I did, update this ROS question and create an issue on the Cartographer issue tracker and link it back here.

Usage is:

$ roslaunch TeamHector_cartographer_2d.launch bagfilename:=/path/to/your/bagfile/bagfile.bag