title: How to make 3D bar plot from dataframe
body: <p>This is how my df looks like:</p>
  <pre><code>hr    slope  value   
  8      s_1     6     
  10     s_1     2     
  8      s_2     4     
  10     s_2     8    
  </code></pre>
  <p>I would like to make a 3D bar plot with 'hr' in the x-axis, 'value' in the y-axis, and 'slopes' in the z-axis.</p>
  <pre><code>xpos = df['hr']
  ypos = df['value']
  xpos, ypos = np.meshgrid(xpos+0.25, ypos+0.25)
  xpos = xpos.flatten()
  ypos = ypos.flatten()
  zpos=np.zeros(df.shape).flatten()
  
  dx=0.5 * np.ones_like(zpos)
  dy=0.5 * np.ones_like(zpos)
  dz=df.values.ravel()
  
  ax.bar3d(xpos,ypos,zpos,dx,dy,dz,color='b', alpha=0.5)
  plt.show()
  </code></pre>
  <p>I get the following error messages:</p>
  <pre><code>ValueError: shape mismatch: objects cannot be broadcast to a single shape
  </code></pre>
  <p>Any help is very welcome,
  thank you in advance</p>