title: Using numpy - header argument invalid
body: <p>I am using numpy in a basic machine learning tutorial and Eclipse with PyDev is throwing the following error:</p>
  
  <pre><code>header='MoleculeId,PredictedProbability', comments = '')
  TypeError: savetxt() got an unexpected keyword argument 'header'
  </code></pre>
  
  <p>I've looked up the <code>numpy.savetxt</code> function and header is included in the structure so Im not sure where the error is. FYI, if I remove the header portion altogether the file runs as required, but I really need it to label my CSV columns.</p>
  
  <p>Here is the code I'm using. </p>
  
  <pre><code>from sklearn.ensemble import RandomForestClassifier
  from numpy import genfromtxt, savetxt
  
  def main():
      #create the training &amp; test sets, skipping the header row with [1:]
      dataset = genfromtxt(open('Data/train.csv','r'), delimiter=',', dtype='f8')[1:]    
      target = [x[0] for x in dataset]
      train = [x[1:] for x in dataset]
      test = genfromtxt(open('Data/test.csv','r'), delimiter=',', dtype='f8')[1:]
  
      #create and train the random forest
      #multi-core CPUs can use: rf = RandomForestClassifier(n_estimators=100, n_jobs=2)
      rf = RandomForestClassifier(n_estimators=100)
      rf.fit(train, target)
      predicted_probs = [[index + 1, x[1]] for index, x in enumerate(rf.predict_proba(test))]
  
      savetxt('Data/submission.csv', predicted_probs, delimiter=',', fmt='%d,%f', 
              header='MoleculeId,PredictedProbability', comments = '')
  
  if __name__=="__main__":
      main()
  </code></pre>