title: Extending colorbar to include out of range data
body: <p>I was trying to make a Polar heatmap using the following code.</p>
  <pre><code># Plotting the polar plot 
  from matplotlib.colorbar import ColorbarBase
  from matplotlib.colors import LogNorm
  import matplotlib.pyplot as plt
  cmap = obspy_sequential 
  
  # Have defined the variables to be used for pointing to the coordinates 
  # baz is angular, slow is radial, abs_power is the value at every co-ordinate
  # Choose number of fractions in plot (desirably 360 degree/N is an integer!)
  N = 72
  N2 = 30
  abins = np.arange(N + 1) * 360. / N
  sbins = np.linspace(0, 3, N2 + 1)
  
  # Sum rel power in bins given by abins and sbins
  hist, baz_edges, sl_edges = \
      np.histogram2d(baz, slow, bins=[abins, sbins], weights=abs_power)
  
  # Transform to radian
  baz_edges = np.radians(baz_edges)
  
  # Add polar and colorbar axes
  fig = plt.figure(figsize=(8, 8))
  cax = fig.add_axes([0.85, 0.2, 0.05, 0.5])
  ax = fig.add_axes([0.10, 0.1, 0.70, 0.7], polar=True)
  ax.set_theta_direction(-1)
  ax.set_theta_zero_location(&quot;N&quot;)
  
  dh = abs(sl_edges[1] - sl_edges[0])
  dw = abs(baz_edges[1] - baz_edges[0])
  
  # Circle through backazimuth
  for i, row in enumerate(hist):
      bars = ax.bar((i * dw) * np.ones(N2),
                    height=dh * np.ones(N2),
                    width=dw, bottom=dh * np.arange(N2),color=cmap(row / hist.max()))
  
  ax.set_xticks(np.linspace(0, 2 * np.pi, 10, endpoint=False))
  ax.set_yticklabels(velocity)
  ax.set_ylim(0, 3)
  [i.set_color('white') for i in ax.get_yticklabels()]
  ColorbarBase(cax, cmap=cmap,
               norm=LogNorm(vmin=hist.min(),vmax=hist.max()))
  plt.show()
  </code></pre>
  <p>I am creating multiple plots like this and thus I need to extend the range of the colorbar beyond the maximum of the abs_power data range.
  I tried changing the vmax and vmin to the maximum-minimum target numbers I want, but it plots out the exact same plot every single time. The maximum value on the colorbar keeps changing but the plot does not change. Why is this happening?
  Here is how it looks,</p>
  <hr />
  <p><a href="https://i.stack.imgur.com/hpL9n.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hpL9n.png" alt="Polar colormap" /></a></p>
  <hr />
  <p>Here the actual maximum power is way lesser than the maximum specified in the colorbar. Still a bright yellow spot is visible.
  PS : I get this same plot for any vmax,vmin values I provide.</p>