Update plot_types barbs to show a more realistic use case

Barbs are a visualization of vector fields and usually plotted on a
regular grid.

Author: timhoffm

plot_types/arrays/barbs.py

@@ -1,28 +1,33 @@
 """
-===========
-barbs(U, V)
-===========
+================
+barbs(X, Y U, V)
+================
 
 See `~matplotlib.axes.Axes.barbs`.
 """
 import matplotlib.pyplot as plt
 import numpy as np
 
-plt.style.use('_mpl-gallery')
+plt.style.use('_mpl-gallery-nogrid')
 
 # make data:
-np.random.seed(1)
-X = [[2, 4, 6]]
-Y = [[1.5, 3, 2]]
-U = np.zeros_like(X)
-V = -np.ones_like(X) * np.linspace(50, 100, 3)
+X, Y = np.meshgrid([1, 2, 3, 4], [1, 2, 3, 4])
+angle = np.pi / 180 * np.array([[15., 30, 35, 45],
+                                [25., 40, 55, 60],
+                                [35., 50, 65, 75],
+                                [45., 60, 75, 90]])
+amplitude = np.array([[5, 10, 25, 50],
+                      [10, 15, 30, 60],
+                      [15, 26, 50, 70],
+                      [20, 45, 80, 100]])
+U = amplitude * np.sin(angle)
+V = amplitude * np.cos(angle)
 
 # plot:
 fig, ax = plt.subplots()
 
-ax.barbs(X, Y, U, V, barbcolor="C0", flagcolor="C0", length=10, linewidth=1.5)
+ax.barbs(X, Y, U, V, barbcolor="C0", flagcolor="C0", length=7, linewidth=1.5)
 
-ax.set(xlim=(0, 8), xticks=np.arange(1, 8),
-       ylim=(0, 8), yticks=np.arange(1, 8))
+ax.set(xlim=(0, 4.5), ylim=(0, 4.5))
 
 plt.show()