title: How to call reorder within aes_string of ggplot
body: <p>I need to reorder a barplot from high to low (left to right) using ggplot &amp; aes_string(). For e.g. for a dataframe df &lt;- f(X,Y,Z) this can be done with</p>
  
  <pre><code> ggplot(top10,aes(x=reorder(X,-Y),y=Y,fill=X) + geom_bar(stat="identity")
  </code></pre>
  
  <p>But I need to achieve this by referring to column numbers of the dataframe instead of column names as shown below</p>
  
  <pre><code> ggplot(top10, aes_string(x=colnames(top10)[num1],y=meanFeat, 
   fill=colnames(top10)[num1])) +  geom_bar(stat="identity")
  </code></pre>
  
  <p>The statement above plots the output using column numbers. However it does not reorder from high to low (left to right)</p>
  
  <p>How can I use the re-order function within aes_string to achieve this?</p>