title: Pandas : TypeError: float() argument must be a string or a number
body: <p>I have a dataframe that contains </p>
  
  <pre><code>user_id    date       browser  conversion  test  sex  age  country
     1    2015-12-03       IE        1         0    M   32.0   US
  </code></pre>
  
  <p>This is my entire code thus far!</p>
  
  <pre><code>data["country"].fillna("missing")
  data["age"].fillna(-10000, inplace=True)
  data["ads_channel"].fillna("missing")
  data["sex"].fillna("missing")
  data['date'] = pd.to_datetime(data.date)
  
  columns = data.columns.tolist()
  columns = [c for c in columns if c not in ["test"]]
  from sklearn import tree
  clf = tree.DecisionTreeClassifier(max_depth=2, min_samples_leaf = (len(data)/100) )
  clf = clf.fit(data[columns],data["test"])
  </code></pre>
  
  <p>I am getting this error:</p>
  
  <pre><code>---------------------------------------------------------------------------
  TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-560-95a8a54aa939&gt; in &lt;module&gt;()
        4 from sklearn import tree
        5 clf = tree.DecisionTreeClassifier(max_depth=2, min_samples_leaf = (len(data)/100) )
  ----&gt; 6 clf = clf.fit(data[columns],data["test"])
  
  C:\Users\SnehaPriya\Anaconda2\lib\site-packages\sklearn\tree\tree.pyc in fit(self, X, y, sample_weight, check_input, X_idx_sorted)
      152         random_state = check_random_state(self.random_state)
      153         if check_input:
  --&gt; 154             X = check_array(X, dtype=DTYPE, accept_sparse="csc")
      155             if issparse(X):
      156                 X.sort_indices()
  
  C:\Users\SnehaPriya\Anaconda2\lib\site-packages\sklearn\utils\validation.pyc in check_array(array, accept_sparse, dtype, order, copy, force_all_finite, ensure_2d, allow_nd, ensure_min_samples, ensure_min_features, warn_on_dtype, estimator)
      371                                       force_all_finite)
      372     else:
  --&gt; 373         array = np.array(array, dtype=dtype, order=order, copy=copy)
      374 
      375         if ensure_2d:
  
  TypeError: float() argument must be a string or a number
  </code></pre>
  
  <p>I am still learning to code and I would like to know how to overcome this error. 
  Any help will be much appreciated!</p>