title: Function to change all variables of factor type to lower case
body: <p>I need to create a function in order to change all my factor variables to lower case.</p>
  
  <p>I've already done that: </p>
  
  <pre><code>change_lower=function(x){if(is.factor(x)) tolower(x)} 
  </code></pre>
  
  <p>But I think I'm doing something wrong, maybe the if isn't good for what I want. Any ideas?</p>