Fix of typos, added explanation for Q.

In response to reader's email.

code/book_plots.py

@@ -86,7 +86,7 @@ def plot_kf_output(xs, filter_xs, zs, title=None, aspect_equal=True):
     if zs is not None:
         plot_measurements(zs)
     show_legend()
-    set_labels(title=title, x='meters', y='time (sec)')
+    set_labels(title=title, y='meters', x='time (sec)')
     if aspect_equal:
         plt.gca().set_aspect('equal')
     plt.xlim((-1, len(xs)))

code/ukf_internal.py

@@ -327,6 +327,8 @@ def plot_scatter_of_bearing_error():
         xs.append(d*math.cos(a))
         ys.append(d*math.sin(a))
     plt.scatter(xs, ys)
+    plt.xlabel('x')
+    plt.ylabel('y')
 
 
 def plot_scatter_moving_target():