title: Generating class name list based on class index list
body: <p>I'm playing with <code>iris_dataset</code> from <code>sklearn.datasets</code>
  I want to generate list similiar to <code>iris_dataset['target']</code> but to have name of class instead of index.
  The way I did it:</p>
  
  <pre><code>from sklearn.datasets import load_iris
  iris_dataset=load_iris()
  y=iris_dataset.target
  print("Iris target: \n {}".format(iris_dataset.target))
  unique_y = np.unique(y)
  class_seq=['']
  class_seq=class_seq*y.shape[0]
  
  for i in range(y.shape[0]):
      for (yy,tn) in zip(unique_y,iris_dataset.target_names):
          if y[i]==yy:
              class_seq[i]=tn          
  
  print("Class sequence: \n {}".format(class_seq))
  </code></pre>
  
  <p>but I would like to do it not looping through all of the elements of <code>y</code>, how to do it better way?</p>
  
  <p>The outcome is that I need this list for <code>pandas.radviz</code> plot to have a proper legend:</p>
  
  <pre><code>pd.plotting.radviz(iris_DataFrame,'class_seq',color=['blue','red','green'])
  </code></pre>
  
  <p>And further to have it for any other dataset.</p>