[chimerax-users] RMSD for all frames in a trajectory

Dear All, I am working with a trajectory of a tetramer. I would like to align the A chains in all frame of the trajectory and then calculate the rmsd of all chains in all frames relative to the respective chain of the first frame (i.e., align only chains A but calculate for all chains), and write the results to a text file. Is that possible? I can do a similar calculation with a script in old Chimera but don’t know how to do it in ChimeraX. I attach the zipped script for old Chimera. Best regards Sasha