title: Replacing commas to periods in all colums in R
body: <p>I am trying to write a function to change the numbers in a column so that the ',' is a '.'</p>
  
  <p>I want to then convert that column into a double.</p>
  
  <p>For example, here is some data to copy/paste:</p>
  
  <pre><code>df &lt;- data.frame(a=c("1,1", "2,2"))
  </code></pre>