title: Python/Scikit-Learn - Can't handle mix of multiclass and continuous
body: <p>I'm trying to fit an SGDRegressor to my data and then check the accuracy. The fitting works fine, but then the predictions are not in the same datatype(?) as the original target data, and I get the error </p>
  
  <pre><code>ValueError: Can't handle mix of multiclass and continuous
  </code></pre>
  
  <p>When calling <code>print "Accuracy:", ms.accuracy_score(y_test,predictions)</code>.</p>
  
  <p>The data looks like this (just 200 thousand + rows):</p>
  
  <pre><code>Product_id/Date/product_group1/Price/Net price/Purchase price/Hour/Quantity/product_group2
  0   107 12/31/2012  10  300 236 220 10  1   108
  </code></pre>
  
  <p>The code is as follows:</p>
  
  <pre><code>from sklearn.preprocessing import StandardScaler
  import numpy as np
  from sklearn.linear_model import SGDRegressor
  import numpy as np
  from sklearn import metrics as ms
  
  msk = np.random.rand(len(beers)) &lt; 0.8
  
  train = beers[msk]
  test = beers[~msk]
  
  X = train [['Price', 'Net price', 'Purchase price','Hour','Product_id','product_group2']]
  y = train[['Quantity']]
  y = y.as_matrix().ravel()
  
  X_test = test [['Price', 'Net price', 'Purchase price','Hour','Product_id','product_group2']]
  y_test = test[['Quantity']]
  y_test = y_test.as_matrix().ravel()
  
  clf = SGDRegressor(n_iter=2000)
  clf.fit(X, y)
  predictions = clf.predict(X_test)
  print "Accuracy:", ms.accuracy_score(y_test,predictions)
  </code></pre>
  
  <p>What should I do differently? Thank you!</p>