title: R changing column names containing plus or brackets
body: <p>I am saving my column names of a <code>data.frame</code> into a variable in <code>R</code>. Some of my columns names contain a plus sign <code>+</code>. <code>R</code> changes the <code>+</code> into a <code>.</code> when saving it into a variable. I would like to retain the <code>+</code> so that i can pick these columns again automatically when I need them.</p>
  
  <p>Here is the command I am using to save the column names into a variable:</p>
  
  <pre><code>for (u in 1:50) {
      k &lt;- colnames[u]
      f &lt;- append(f,k)
  }
  ## f is defined previously in my program
  </code></pre>
  
  <p>Here is the command I am using to get the names I need again:</p>
  
  <pre><code>file2 &lt;- file1[,f]
  </code></pre>
  
  <p><strong>Example:</strong> <code>column1+</code> is named <code>column1.</code> in the variable <code>f</code>  </p>
  
  <p><strong>Note:</strong> This happened to the brackets <code>()</code> as well as slashes <code>/</code></p>
  
  <p>Any Ideas how I can get around this problem?</p>