title: tfidf vectorizer giving wrong results
body: <p>I have documents like below</p>
  
  <pre><code>1             NAME LASTNAME DOB CITY
  2                     NAME ADDRESS CITY
  3            NAME LASTNAME ADDRESS CITY
  4    NAME LASTNAME ADDRESS CITY PINCODE
  5                  NAME ADDRESS PINCODE
  </code></pre>
  
  <p>and <code>TfidfVectorizer</code> gave below values</p>
  
  <pre><code>    address      city      dob  employername  lastname  mobile      name  \
  0  0.000000  0.306476  0.68835           0.0  0.553393     0.0  0.354969   
  1  0.573214  0.535492  0.00000           0.0  0.000000     0.0  0.620221   
  2  0.412083  0.384964  0.00000           0.0  0.695116     0.0  0.445875   
  3  0.357479  0.333954  0.00000           0.0  0.603009     0.0  0.386795   
  4  0.493437  0.000000  0.00000           0.0  0.000000     0.0  0.533901   
  
     phone   pincode  
  0    0.0  0.000000  
  1    0.0  0.000000  
  2    0.0  0.000000  
  3    0.0  0.497447  
  4    0.0  0.686637  
  </code></pre>
  
  <p>From above, both documents 1 &amp; 3 have 'name' term and also no. of terms is same in both documents, so tf(name) should be same in both cases. Also idf would be same. But why 'name' feature has different tfidf values in both documents?</p>
  
  <p>Please help me understand this.</p>
  
  <p>I actually have many documents and applied tfidf on all of those, given above are top 5 records of data.</p>