title: NameError: name 'labels_true' is not defined for dbscan
body: <p>I am using a template script and trying to feed in my data. However, I am not sure what labels_true implies as the error states that is it undefined. </p>
  
  <p>Here is my data array:</p>
  
  <pre><code>data=array([[5.71585827e+00, 3.32320000e+04],
         [0.00000000e+00, 0.00000000e+00],
         [0.00000000e+00, 0.00000000e+00],
         ...,
         [9.57746479e-02, 3.40000000e+01],
         [7.01388889e-01, 1.01000000e+02],
         [9.70350404e-02, 3.60000000e+01]])
  </code></pre>
  
  <p>Now I am applying this script:</p>
  
  <pre><code>import numpy as np
  from sklearn.cluster import DBSCAN
  from sklearn import metrics
  from sklearn.preprocessing import StandardScaler
  
  
  # #############################################################################
  
  X=data
  X = StandardScaler().fit_transform(X)
  
  # #############################################################################
  # Compute DBSCAN
  db = DBSCAN(eps=0.3, min_samples=10).fit(X)
  labels = db.labels_ 
  
  print("Homogeneity: %0.3f" % metrics.homogeneity_score(labels_true, labels))
  
  
  NameError: name 'labels_true' is not defined
  </code></pre>