title: Does tm automatically ignore the very short strings?
body: <p>Here is my code:
  example 1:</p>
  
  <pre><code>a &lt;- c("ab cd de","ENERGIZER A23 12V ALKALINE BATTERi")
  a1 &lt;- VCorpus(VectorSource(a))
  a2 &lt;- TermDocumentMatrix(a1,control = list(stemming=T))
  inspect(a2)
  </code></pre>
  
  <p>The result is:</p>
  
  <pre><code>         Docs
  Terms     1 2
    12v     0 1
    a23     0 1
    alkalin 0 1
    batteri 0 1
    energ   0 1
  </code></pre>
  
  <p>Looks like the first string in a is ignored. </p>
  
  <p>example 2</p>
  
  <pre><code>a &lt;- c("abcd cde de","ENERGIZER A23 12V ALKALINE BATTERi")
  a1 &lt;- VCorpus(VectorSource(a))
  a2 &lt;- TermDocumentMatrix(a1,control = list(stemming=T))
  inspect(a2)
  </code></pre>
  
  <p>The result is:</p>
  
  <pre><code>         Docs
  Terms     1 2
    12v     0 1
    a23     0 1
    abcd    1 0
    alkalin 0 1
    batteri 0 1
    cde     1 0
    energ   0 1
  </code></pre>
  
  <p>We can see two sub-strings (abcd, cde) are kept while the shorest one (de) is still missing. The situation is the same if I do not use control = list(stemming=T). So, I am curious if this is a sort of definition in tm? The strings will be ignored if it is less than 3 letters? I do not think this is a good idea. It is very possible that a string is useful even it is short such as abbreviation. </p>
  
  <p>If so, is there a parameter or something that can change this? Thanks a lot.</p>