title: Decision Tree produces different outputs
body: <p>I am currently using decision trees (using Scikit Learn) to predict certain values. The problem I'm facing is that the output of the algorithm is not consistent. Is this a property of Decision Trees? On multiple runs (with no change to data/algorithm) I get different results. </p>
  
  <p>I used Scikit's Decision Tree Class without changing anything to start with</p>
  
  <pre><code>svr = DecisionTreeRegressor()
  </code></pre>
  
  <p>Then, to remove any 'randomness', I changed it to</p>
  
  <pre><code>svr = DecisionTreeRegressor(splitter='best', random_state=None)
  </code></pre>
  
  <p>What is causing the different results? And how do I prevent them?</p>
  
  <p>Two of the results being (plotted for simplicity) 
  Red is DTR results. Blue is the test set.</p>
  
  <p><a href="https://i.stack.imgur.com/rvBEV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rvBEV.png" alt="Image One"></a></p>
  
  <p><a href="https://i.stack.imgur.com/vKt5q.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vKt5q.png" alt="Image Two"></a></p>