title: R text mining - intersection between text fields
body: <p>I was wondering if there's a quick way to find directed intersection between 2 text strings e.g. </p>
  
  <pre><code> t1 &lt;- "I have achieved my goals over the past 20 years and look forward for my next chalanges"
   t2 &lt;- " have achieved goals and look my chalanges some other words bla bla"
  </code></pre>
  
  <p>t1 isContainedIn t2 would return 7 because 7 words that apeared in t1 also apeared in t2 .
  Also, t1 and t2 are 2 columns in a data frame, so I would need to apply that function on the entire data frame and attached the result column to my original data frame.
  This is how my data frame 'data.selected' looks like:</p>
  
  <pre><code>        keywords                                         title
  1  Samsung UN48H6350 48" Samsung UN48H6350 48" Full 1080p Smart HDTV 120Hz with Wi-Fi +$50 Visa Gift Card
  2  Samsung UN48H6350 48"     Samsung UN48H6350 48" Full HD Smart LED TV -Bundle- (See Below for Contents)
  3  Samsung UN48H6350 48"      Samsung UN48H6350 48" Class Full HD Smart LED TV -BUNDLE- See below Details
  4  Samsung UN48H6350 48"     Samsung UN48H6350 48" Full HD Smart LED TV With BD-H5100 Blu-ray Disc Player
  5  Samsung UN48H6350 48"                 Samsung UN48H6350 48" Smart 1080p Clear Motion Rate 240 LED HDTV
  6  Samsung UN48H6350 48"            Samsung UN48H6350 - 48-Inch Full HD 1080p Smart HDTV 120Hz with Wi-Fi
  7  Samsung UN48H6350 48"               Samsung 6350 Series UN48H6350 48" 1080p HD LED LCD Internet TV NEW
  8  Samsung UN48H6350 48"  Samsung Un48h6350af 75" 1080p Led-lcd Tv - 16:9 - Hdtv 1080p - (un75h6350afxza)
  9  Samsung UN48H6350 48"                         Samsung UN48H6350 - 48" HD 1080p Smart HDTV 120Hz Bundle
  10 Samsung UN48H6350 48"   Samsung UN48H6350 - 48-Inch Full HD 1080p Smart HDTV 120Hz with Wi-Fi, (R#416)
  </code></pre>