%matplotlib inline
import matplotlib.pyplot as plt
import numpy as np
from mpl_toolkits.mplot3d.axes3d import Axes3D

def plot(t, r, w, dx, dy, ph):
    rx = np.arange(-r, r, w)
    ry = np.arange(-r, r, w)
    c = 1 if ph is None else 2
    fig = plt.figure(figsize=(c * 9 - 4, 5))
    fig.suptitle(t)

    if ph is not None:
        ax = fig.add_subplot(1, 2, 1, projection='3d')

        x, y, z = np.meshgrid(rx, ry, 0)
        ax.quiver(x, y, z, dx(x, y), dy(x, y), 0, length=w, color='red', normalize=True)

        x, y = np.meshgrid(rx, ry)
        ax.plot_surface(x, y, ph(x, y), cmap=plt.cm.bone)

    ax = fig.add_subplot(1, c, c)

    if ph is not None:
        r2 = np.arange(-r, r, w / 4)
        x, y = np.meshgrid(r2, r2)

        cs1 = ax.contourf(x, y, ph(x, y), 10, cmap=plt.cm.bone)
        #cs2 = ax.contour(cs1, colors='b')

        cbar = plt.colorbar(cs1)
        #cbar.add_lines(cs2)

    x, y = np.meshgrid(rx, ry)
    ax.quiver(x, y, dx(x, y), dy(x, y), color='red')