title: Non alphanumeric characters in R
body: <p>For uppercase, lowercase letters and 10-digits I can generate a vector that contains all letters or 10-digit number as follow:</p>
  
  <pre><code>A &lt;- LETTERS[0:26]
  B &lt;- letters[0:26]
  C &lt;- seq(0,9)
  </code></pre>
  
  <p>I wonder whether there is a similar function for non-alphanumeric characters.</p>
  
  <pre><code>~!@#$%^&amp;*_-+=`|\(){}[]:;"'&lt;&gt;,.?/
  </code></pre>
  
  <p>I tried </p>
  
  <pre><code>D &lt;- c("~","!","@","#","$","%","^", "&amp;","*","_","-","+","=","`","|","\","(",")","{","}","[","]",":",";",""","'","&lt;","&gt;",",",".","?","/")
  </code></pre>
  
  <p>Thanks</p>