title: How to extract frequency from R table using vector of arguments
body: <p>I have a table, for example:</p>
  <pre><code>tbl &lt;- table(iris[, 1:3])
  </code></pre>
  <p>I can extract frequency from the table this way:</p>
  <pre><code>tbl[['4.6', '3.6', '1']]
  </code></pre>
  <p>How to do the same if my values stored as vector</p>
  <pre><code>vars &lt;- c('4.6', '3.6', '1')
  </code></pre>
  <p>In fact <code>vars</code> is named vector and I need general way to extract from tables.</p>