title: Select multiple columns with dplyr::select() with numbers as names
body: <p>Let's say I have the following data frame:</p>
  
  <pre><code>a &lt;- runif(10)
  dd &lt;- as.data.frame(t(a))
  names(dd) &lt;- c("ID", "a", "a2", "b", "b2", "f", "XXX", "1", "4", "8")
  </code></pre>
  
  <p>In <code>dplyr</code>, there is a nice way to select a number of columns. For example, to select the columns between column <strong>a</strong> and column <strong>f</strong>, I can use</p>
  
  <pre><code>dd %&gt;% dplyr::select(a:f)
  </code></pre>
  
  <p>In my problem, the columns of the last part of the data frame may vary, yet they always have as name a number between 1 and 99. However, I can not seem to be able to do the same trick as above:</p>
  
  <pre><code>&gt; dd %&gt;% select(1:99)
  Error: Position must be between 0 and n
  &gt; dd %&gt;% select("1":"99")
  Error: Position must be between 0 and n
  </code></pre>
  
  <p>Which is because using <code>select()</code> tries to select columns by position in this way. </p>
  
  <p>I would like to be able to obtain a data frame with all columns between <strong>a</strong> and <strong>f</strong>, and those with labels that are numbers between <strong>1</strong> and <strong>99</strong>. Is that possible to do in one go with <code>select()</code>?</p>