Handles interpolating irregular data to a grid,
  and plots it using the given func [default: contourf]
  See http://wiki.scipy.org/Cookbook/Matplotlib/Gridding_irregularly_spaced_data

def irregular_contour(x, y, z, func=plt.contourf, func_kwargs=dict(),
                      grid_size=(100,100), padding_fraction=0.05,
                      interp_method='nearest'):
  '''Handles interpolating irregular data to a grid,
  and plots it using the given func [default: contourf]
  See http://wiki.scipy.org/Cookbook/Matplotlib/Gridding_irregularly_spaced_data
  '''
  from scipy.interpolate import griddata  # Late import; scipy is optional
  x, y, z = map(np.asanyarray, (x, y, z))
  x_range = (x.min(), x.max())
  y_range = (y.min(), y.max())
  pad_x = padding_fraction * -np.subtract.reduce(x_range)
  pad_y = padding_fraction * -np.subtract.reduce(y_range)
  grid_x = np.linspace(x_range[0] - pad_x, x_range[1] + pad_x, grid_size[0])
  grid_y = np.linspace(y_range[0] - pad_y, y_range[1] + pad_y, grid_size[1])
  grid_z = griddata((x, y), z, (grid_x[None], grid_y[:,None]),
                    method=interp_method)
  return func(grid_x, grid_y, grid_z, **func_kwargs)