title: Plot every column in a data frame as a histogram on one page using ggplot
body: <p>I would like to plot each column of a data.frame using a histogram on one page.  Here is an example using the sample "diamonds" data set which comes with R:</p>
  
  <pre><code>p = list()
  for (i in 1:ncol(diamonds)) p[[i]] &lt;- qplot(diamonds[,i], xlab=names(diamonds)[[i]])
  do.call(grid.arrange, p)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/VJLp7.png" alt="enter image description here"></p>
  
  <p>This does plot all the columns, but the data looks the same in each one.  So, something is clearly wrong.</p>
  
  <p>Is this the right approach for this task?  I'm sure I have some silly syntax somewhere that is assigning the same column data set to each element in the list, but I'm not sure what it is.</p>
  
  <p>Thank you</p>