title: What is the negative mean absolute error in scikit-learn?
body: <p>I am trying to train a model using SciKit Learn's SVM module. For the scoring, I could not find the <code>mean_absolute_error</code>(MAE), however, <code>negative_mean_absolute_error</code>(NMAE) does exist. What is the difference between these 2 metrics? Lets say I get the following results for 2 models:</p>
  
  <p><code>model 1 (NMAE = -2.6), model 2(NMAE = -3.0)</code></p>
  
  <p>Which model is better? Is it model 1?</p>
  
  <p>Moreover, how does the negative compare to the positive? Say the following:</p>
  
  <p><code>model 1 (NMAE = -1.7), model 2(MAE = 1.4)</code></p>
  
  <p>Here, which model is better?</p>