title: Input file format for email classification with svm-light
body: <p>I am working with email subject, so I have 20 emails i want to classify, and a file with 20 lines - one line has one email subject.I have been working on it, but I am unable to figure out what the features refer to and the format of the input file for svmlight. Any tips to proceed will be helpful. Thanks in advance!</p>
  
  <p>I have taken the tf-idf of the first 500 subject lines as a trial. However, according to svm-light format, we need:</p>
  
  <pre><code>&lt;line&gt; .=. &lt;target&gt; &lt;feature&gt;:&lt;value&gt; &lt;feature&gt;:&lt;value&gt; ... &lt;feature&gt;:&lt;value&gt; # &lt;info&gt;
  </code></pre>
  
  <p>I have only the tf-idf features for 500 lines. Sadly, this is not read by the svm-light as it needs features/value pair. Any ideas on what the value could be or how I can change the file in order to be read?</p>
  
  <p>An idea of the file I have(first 5 email features):</p>
  
  <pre><code>1 201 1.0
  2 280 0.123165672613
  2 313 0.343915400191
  2 515 0.157569797284
  2 588 0.343915400191
  2 652 0.343915400191
  2 657 0.343915400191
  2 774 0.23622904941
  2 921 0.283118375032
  2 1158 0.254849368195
  2 1240 0.343915400191
  2 1348 0.343915400191
  2 1362 0.222321349873
  3 57 0.342220321154
  3 185 0.391349077827
  3 244 0.391349077827
  3 300 0.391349077827
  3 693 0.391349077827
  3 730 0.342220321154
  3 1391 0.391349077827
  4 57 0.342220321154
  4 185 0.391349077827
  4 244 0.391349077827
  4 300 0.391349077827
  4 693 0.391349077827
  4 730 0.342220321154
  4 1391 0.391349077827
  5 32 0.323558487577
  5 102 0.323558487577
  5 157 0.364177022553
  5 160 0.364177022553
  5 718 0.151013895297
  5 1171 0.364177022553
  5 1277 0.323558487577
  5 1308 0.364177022553
  5 1336 0.364177022553
  </code></pre>
  
  <p>Any ideas would be really appreciated, as I have been stuck at this point for quite long now. Thanks in advance!</p>