title: Python: Dendogram with Scipy doesn´t work
body: <p>I want to use the dendogram of scipy.
  I have the following data:</p>
  
  <p>I have a list with seven different means. For example: </p>
  
  <pre><code>Y = [71.407452200146807, 0, 33.700136456196823, 1112.3757110973756, 31.594949722819372, 34.823881975554166, 28.36368420190157]
  </code></pre>
  
  <p>Each mean is calculate for a different user. For example: </p>
  
  <pre><code>X = ["user1", "user2", "user3", "user4", "user5", "user6", "user7"]
  </code></pre>
  
  <p>My aim is to display the data described above with the help of a dendorgram. </p>
  
  <p>I tried the following:</p>
  
  <pre><code>Y = [71.407452200146807, 0, 33.700136456196823, 1112.3757110973756, 31.594949722819372, 34.823881975554166, 28.36368420190157]
  X = ["user1", "user2", "user3", "user4", "user5", "user6", "user7"]
  
  # Attempt with matrix
  #X = np.concatenate((X, Y),)
  #Z = linkage(X)
  
  Z = linkage(Y)
  # Plot the dendogram with the results above
  dendrogram(Z, leaf_rotation=45., leaf_font_size=12. , show_contracted=True)
  plt.style.use("seaborn-whitegrid")
  plt.title("Dendogram to find clusters")
  plt.ylabel("Distance")
  plt.show()
  </code></pre>
  
  <p>But it says:</p>
  
  <blockquote>
    <p>ValueError: Length n of condensed distance matrix 'y' must be a binomial coefficient, i.e.there must be a k such that (k \choose 2)=n)!</p>
  </blockquote>
  
  <p>I already tried to convert my data into a matrix. With:</p>
  
  <pre><code># Attempt with matrix
  #X = np.concatenate((X, Y),)
  #Z = linkage(X)
  </code></pre>
  
  <p>But that doesn´t work too!</p>
  
  <p>Are there any suggestions? </p>
  
  <p>Thanks :-)</p>