title: Issue with ggplot and geom_bar: want two columns to stack without adding together
body: <p>I'm making a bar graph showing how many votes and candidate got in two elections. I want the values stacked, but the values are adding together to make the y axis bigger than it should be. So for example, in the x=23 spot, the 2018 value should only be about 800. the 2019 value is correct, but the two are being added together to make the 2019 value bigger than it should be.</p>
  
  <p><img src="https://i.stack.imgur.com/tywpo.png" alt="enter image description here"></p>
  
  <p>I don't understand how to get it so that it shows me the 2018 value with the 2019 value stacked inside of it without adding the two together.</p>
  
  <p>Here is the code I'm using:</p>
  
  <pre><code>ggplot(data = OverallMcCreadyVotes, aes(x=precinct_abbrv, y=McCready,fill=year)) +
    geom_bar(stat = "identity") +
    scale_fill_manual(
      breaks = c("2019","2018"),
      values = c("dark blue","light blue")
    )
  </code></pre>