changed as per suggestions from Jason and Timo

examples-gallery/plot_parallel_park.py

@@ -1,4 +1,3 @@
-# %%
 """
 Parallel Park a Car
 ===================
@@ -174,7 +173,8 @@
 prob.add_option('nlp_scaling_method', 'gradient-based')
 
 # %%
-# Give some rough estimates for the x and y trajectories.
+# Give some rough estimates for the x and y trajectories. They were used to
+# generate the initial guess, now stored in the file parallel_park_solution.npy.
 x_guess = 3.0/duration*2.0*time
 x_guess[num_nodes//2:] = 6.0 - 3.0/duration*2.0*time[num_nodes//2:]
 y_guess = 2.0/duration*time
@@ -185,15 +185,17 @@
 prob.plot_trajectories(initial_guess)
 
 # %%
-# Find the optimal solution.
+# Solve the optimisation, using the initial guess stored in the file
+# parallel_park_solution.npy.
 initial_guess = np.load('parallel_park_solution.npy')
 solution, info = prob.solve(initial_guess)
 print(info['status_msg'])
 print(info['obj_val'])
 
 # %%
-#Improved initial_guess is stored like this
+#Improved initial_guess may be saved and stored like this:
 # ```np.save('parallel_park_solution.npy', solution)```
+
 # %%
 # Plot the optimal state and input trajectories.
 prob.plot_trajectories(solution)
@@ -230,17 +232,6 @@
     coords.append(eval_point_coords(xi, ui, list(par_map.values())))
 coords = np.array(coords)  # shape(501, 3, 5)
 
-coords1 = []
-time1 = []
-for i in range(coords.shape[0]):
-    if i % 3 == 0:
-        coords1.append(coords[i, :, :])
-        time1.append(time[i])
-coords1.append(coords[-1, :, :])
-time1.append(time[-1])
-time = np.array(time1)
-coords = np.array(coords1)
-
 def frame(i):
 
     fig, ax = plt.subplots()
@@ -267,6 +258,8 @@ def frame(i):
 
 fig, title_text, lines, Pr_path, Pf_path = frame(0)
 
+time = list(time)
+time[-3:] = [time[-1]]*3
 
 def animate(i):
     title_text.set_text('Time = {:1.2f} s'.format(time[i]))
@@ -275,13 +268,13 @@ def animate(i):
     Pf_path.set_data(coords[:i, 0, 2], coords[:i, 1, 2])
 
 
-ani = animation.FuncAnimation(fig, animate, len(time),
-                              interval=int(interval_value*1000*1))
+ani = animation.FuncAnimation(fig, animate, range(0, len(time), 3),
+                              interval=int(interval_value*1000*2))
 
 # %%
 # A frame from the animation.
 
 # sphinx_gallery_thumbnail_number = 7
-frame(140)
+frame(450)
 
 plt.show()