title: XGBoost predictions output not binary?
body: <p>i'm trying to run a very simple example where XGBoost takes some data and do a binary classification. The <a href="https://github.com/dmlc/xgboost/blob/master/doc/parameter.md#learning-task-parameters" rel="nofollow noreferrer">documentation</a> says that xgboost outputs the probabilities when "binary:logistic" is used </p>
  
  <pre><code>import numpy as np
  import xgboost as xgb
  
  data = np.random.rand(7,10)
  label = np.random.randint(2,size=7)
  #print data
  #print label
  
  dtrain = xgb.DMatrix(data, label=label)
  param = {'bst:max_depth':2, 'bst:eta':1, 'silent':1, 'objective':'binary:logistic' }
  plst = param.items()
  
  bst = xgb.train(plst,dtrain,)
  
  dtest= xgb.DMatrix(np.random.rand(4,10))
  ypred = bst.predict(dtest)
  
  print ypred
  </code></pre>
  
  <p>The output is:</p>
  
  <pre><code>[ 0.31350434  0.31350434  0.31350434  0.31350434]
  </code></pre>
  
  <p>So what does this output mean? Does it mean that i've a 31 % chance of getting 1?</p>
  
  <p>How do I translate it to 0,1?</p>
  
  <p>This <a href="https://stackoverflow.com/questions/35826948/xgboost-script-is-not-outputing-binary-properly">question</a> seems related, but i cannot get anything useful out of it.</p>