When we perform molecular dynamics (MD) simulations, sometimes we want to store a frame every time step, in order to increase the quality of the statistics (i.e. when calculating radial distribution functions). But on the other hand, due to their big size, these trajectories might be very difficult to handle by visualization programs (VMD, jmol, …), because they usually load the hole file into memory, and storing every frame (or each few frames) in a long MD with a lot of atoms can produce a trajectory file of several MB or even GB.

The solution: shrinking the big trajectory into a smaller one with my “shrink_traj” script.
This script takes a trajectory file (in xyz format) and copies each nth frame to another file, resulting on a smaller and easier to handle file specially suitable for visualization.