title: Error when trying to convert dotfile of decision tree visualization of DecisionTreeRegression to .png file
body: <p>I have been trying to convert the final decision tree visualization dotfile to .png file using graphviz in python.</p>
  
  <p>But It gives me an error below. I am not sure what I have been doing wrong.</p>
  
  <p>Any help will be appreciated.</p>
  
  <p>Thanks,</p>
  
  <p>Saul</p>
  
  <p><b>Code:</b></p>
  
  <pre><code>import numpy as np
  
  import matplotlib.pyplot as plt 
  
  from sklearn.tree import DecisionTreeRegressor  
  
  from sklearn.tree import export_graphviz
  
  from subprocess import call
  
  from IPython.display import Image
  
  import pydotplus
  
  from subprocess import check_call
  
  import graphviz
  
  dataset = np.array( 
  [['Asset Flip', 100, 1000], 
  ['Text Based', 500, 3000], 
  ['Visual Novel', 1500, 5000], 
  ['2D Pixel Art', 3500, 8000], 
  ['2D Vector Art', 5000, 6500], 
  ['Strategy', 6000, 7000], 
  ['First Person Shooter', 8000, 15000], 
  ['Simulator', 9500, 20000], 
  ['Racing', 12000, 21000], 
  ['RPG', 14000, 25000], 
  ['Sandbox', 15500, 27000], 
  ['Open-World', 16500, 30000], 
  ['MMOFPS', 25000, 52000], 
  ['MMORPG', 30000, 80000] 
  ]) 
  
  
  X= dataset[:,1:2].astype(int) #covert to integer
  
  y = dataset[:, 2].astype(int)  
  
  reg = DecisionTreeRegressor(random_state=0)
  
  reg.fit(X,y)
  
  pred_case = reg.predict([[3750]])
  
  print("Predicted price: % d\n"% pred_case)  
  
  X_grid = np.arange(min(X), max(X), 0.01)
  X_grid = X_grid.reshape((len(X_grid), 1))
  plt.scatter(X, y, color='red')
  
  plt.plot(X_grid, reg.predict(X_grid), color = 'blue')  
  
  plt.title('Profit to Production Cost (Decision Tree Regression)')  
  
  plt.xlabel('Production Cost') 
  
  plt.ylabel('Profit') 
  
  plt.show() 
  
  dotfile = export_graphviz (reg, out_file = None, feature_names =        ['Production Cost'])
  
  graph = graphviz.Source(dotfile)
  graph.render('dtree_render', view=True)
  </code></pre>
  
  <p><b>Error:</b></p>
  
  <p>Traceback (most recent call last):</p>
  
  <p>File "", line 1, in 
      runfile('/home/saul/pythonWork/DTRegressor_test.py', wdir='/home/saul/pythonWork')</p>
  
  <p>File "/home/saul/anaconda3/lib/python3.7/site-packages/spyder_kernels/customize/spydercustomize.py", line 786, in runfile
      execfile(filename, namespace)</p>
  
  <p>File "/home/saul/anaconda3/lib/python3.7/site-packages/spyder_kernels/customize/spydercustomize.py", line 110, in execfile
      exec(compile(f.read(), filename, 'exec'), namespace)</p>
  
  <p>File "/home/saul/pythonWork/DTRegressor_test.py", line 82, in 
      graph.render('dtree_render', view=True)</p>
  
  <p>File "/home/saul/.local/lib/python3.7/site-packages/graphviz/files.py", line 188, in render
      rendered = backend.render(self._engine, format, filepath, renderer, formatter)</p>
  
  <p>File "/home/saul/.local/lib/python3.7/site-packages/graphviz/backend.py", line 183, in render
      run(cmd, capture_output=True, check=True, quiet=quiet)</p>
  
  <p>File "/home/saul/.local/lib/python3.7/site-packages/graphviz/backend.py", line 150, in run
      raise ExecutableNotFound(cmd)</p>
  
  <p>ExecutableNotFound: failed to execute ['dot', '-Tpdf', '-O', 'dtree_render'], make sure the Graphviz executables are on your systems' PATH</p>