Add default values to arguments

Add default values to arguments of function `plot_velocity`.

Inst_eddies/Analysis/plot_velocity.py

@@ -15,7 +15,7 @@ import netCDF4
 import wind_cartopy
 
 
-def plot_velocity(input_file, window, undefined, scale):
+def plot_velocity(input_file, window=None, undefined=False, scale=20):
     with netCDF4.Dataset(input_file) as f:
         if "lon" in f.variables:
             lon = "lon"