title: TypeError: only size-1 arrays can be converted to Python scalars for mesh grid
body: <p>I am trying to plot a contour for an electric potential.</p>
  <p>This is my code :</p>
  <pre><code>z4 = np.linspace(1,10,10)
  X4, Z4 = np.meshgrid(x4, z4)
  vf = (1 / (1.112e-10))*math.log(((5 + (5**2 + X4 + Z4**2)**0.5))/(-5 + (5**2 +X4 + Z4**2)**0.5))
  ax.contour3D(X4, Z4, vf, 50, cmap='binary')
  ax.set_xlabel('x')
  ax.set_ylabel('y')
  ax.set_zlabel('z');
  </code></pre>
  <p>I get this error: TypeError: only size-1 arrays can be converted to Python scalars</p>
  <p>The problem is that I need to keep the meshgrid 2D form as you can't plot a contour with a 1D variable for the contours.</p>