title: altering the color of one value in a ggplot histogram
body: <p>I have a simplified dataframe</p>
  
  <pre><code>library(ggplot2)
  df &lt;- data.frame(wins=c(1,1,3,1,1,2,1,2,1,1,1,3))
  ggplot(df,aes(x=wins))+geom_histogram(binwidth=0.5,fill="red")
  </code></pre>
  
  <p>I would like to get the final value in the sequence,3, shown with either a different fill or alpha. One way to identify its value is</p>
  
  <pre><code>tail(df,1)$wins
  </code></pre>
  
  <p>In addition, I would like to have the histogram bars  shifted so that they are centered over the number. I tried unsuccesfully subtracting from the wins value</p>