title: histogram and density in R by ggplot
body: <p>I have a sales data with value from 1 to 3000000. Most counts are in the interval of [1,800]. If I use the following code to plot histogram: </p>
  
  <p><code>ggplot(his_data) +
    geom_histogram(aes(x = sales), fill = "grey", color = "black")</code></p>
  
  <p>Then the graph looks like:</p>
  
  <p><img src="https://i.stack.imgur.com/JIr74.jpg" alt="histogram"></p>
  
  <p>Is it caused by too spreaded bins?  How could I fix such a problem and add density function as well?</p>
  
  <p>Many thanks.</p>