diff --git a/Trajectories/Analysis/plot_traj.py b/Trajectories/Analysis/plot_traj.py
index 4c16cbb323b80441155a9cbf9716a16670156d58..64443e0f7b67576ca74039ff1559522f3e3adaf6 100755
--- a/Trajectories/Analysis/plot_traj.py
+++ b/Trajectories/Analysis/plot_traj.py
@@ -1,5 +1,10 @@
 #!/usr/bin/env python3
 
+"""This script plots on a map lines linking extrema in trajectories
+and markers for the extrema. The color changes with the trajectory.
+
+"""
+
 import random
 
 import numpy as np
@@ -107,6 +112,7 @@ if __name__ == "__main__":
 
     with open(args.expanded_traj) as f:
         expanded_traj = json.load(f)
+
     print("Number of trajectories:", len(expanded_traj["traj"]))
     SHPC = util_eddies.SHPC_class(
         args.SHPC, def_orient=expanded_traj["orientation"]