Bug fix: correct name of argument

The global variable was used in the body of the function.

Trajectories/cost_function.py

@@ -55,7 +55,7 @@ def calculate_radii_rossby(properties):
     if n_valid_Rossby != 0: avg_Rossby /= n_valid_Rossby
     return avg_rad, avg_Rossby
 
-def get_slice(array_d_ini, date_index):
+def get_slice(array_d_init, date_index):
     i_slice = bisect.bisect(array_d_init, date_index) - 1
     assert i_slice >= 0
     return i_slice