title: Creating bar borders for a stacked histogram in R
body: <p>I have a set of data:</p>
  
  <pre><code>DF &lt;- read.table(text="Rank F1     F2     F3
  1    500    250    50
  2    400    100    30
  3    300    155    100
  4    200    90     10", header=TRUE)
  
  library(reshape2)
  DF1 &lt;- melt(DF, id.var="Rank")
  </code></pre>
  
  <p>I want to create a stacked histogram:</p>
  
  <pre><code>library(ggplot2)
  ggplot(DF1, aes(x = Rank, y = value, fill = variable)) + 
  geom_bar(stat = "identity")
  </code></pre>
  
  <p>Now I want to include a black border for each bar so that it is clearer visually.  I though this would work:</p>
  
  <pre><code>ggplot(DF1, aes(x = Rank, y = value, fill = variable)) + 
  geom_bar(stat = "identity")+geom_histogram(colour = "black")
  </code></pre>
  
  <p>However, this is not what I want.<br>
  Issue 1: there is no black border in each bar.<br>
  Issue 2: there is an extra diagonal line for each group in the legend.  I want to remove this line.</p>
  
  <p>I wonder if anyone can let me know what I have done wrong and what is the correct way to include a black border for each bar in the histogram.</p>
  
  <p>Many thanks.  </p>