Remove intermediate variables

Remove intermediate variables `first_pos` and `last_pos`.

cost_function.py

@@ -154,15 +154,12 @@ for n in g.vertices():
                                        last['date_index'],
                                        last['eddy_index'])
 
-    # grab the centers:
-    first_pos = handlers[first_SHPC]["readers"]["extremum"]\
-        .shape(first_loc).points[0]
-    last_pos = handlers[last_SHPC]["readers"]["extremum"]\
-        .shape(last_loc).points[0]
-
-    # Store positions in the vertex properties:
-    g.vp.pos_first[n] = first_pos # [deg, deg]
-    g.vp.pos_last[n] = last_pos # [deg, deg]
+    # Grab the positions of the extrema and store them in the vertex
+    # properties:
+    g.vp.pos_first[n] = handlers[first_SHPC]["readers"]["extremum"]\
+        .shape(first_loc).points[0] # [in degrees]
+    g.vp.pos_last[n] = handlers[last_SHPC]["readers"]["extremum"]\
+        .shape(last_loc).points[0] # [in degrees]
 
     if (num_of_days > num_of_days_to_avg):
         # The segment is longer than the number of days over which to average