title: How to correctly generate a 3d histogram using numpy or matplotlib built in functions in python?
body: <p>This is more of a general question about 3d histogram creation in python. </p>
  
  <p>I have attempted to create a 3d histogram using the X and Y arrays in the following code</p>
  
  <pre><code>import matplotlib
  import pylab
  import numpy as np
  import matplotlib.pyplot as plt
  from mpl_toolkits.mplot3d.axes3d import Axes3D
  from matplotlib import cm
  
  def threedhist():
      X = [1, 3, 5, 8, 6, 7, 1, 2, 4, 5]
      Y = [3, 4, 3, 6, 5, 3, 1, 2, 3, 8]
      fig = pylab.figure()
      ax = Axes3D(fig)
      ax.hist([X, Y], bins=10, range=[[0, 10], [0, 10]])
      plt.xlabel('X')
      plt.ylabel('Y')
      plt.zlabel('Frequency')
      plt.title('Histogram')
      plt.show()
  </code></pre>
  
  <p>However, I am getting the following error</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;pyshell#0&gt;", line 1, in &lt;module&gt;
      a3dhistogram()
    File "C:/Users/ckiser/Desktop/Projects/Tom/Python Files/threedhistogram.py", line 24, in a3dhistogram
      ax.hist([X, Y], bins=10, range=[[0, 10], [0, 10]])
    File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 7668, in hist
      m, bins = np.histogram(x[i], bins, weights=w[i], **hist_kwargs)
    File "C:\Python27\lib\site-packages\numpy\lib\function_base.py", line 169, in histogram
      mn, mx = [mi+0.0 for mi in range]
  TypeError: can only concatenate list (not "float") to list
  </code></pre>
  
  <p>I have tried the code with and without the "[" in the line
  ax.hist([X, Y], bins=10, range=[[0, 10], [0, 10]])
  I have also tried the function from numpy without success
  H, xedges, yedges = np.histogram2d(x, y, bins = (10, 10))
  Am I missing a step or a parameter?  Any advice would be greatly appreciated.</p>