title: Center x and y axis with ggplot2
body: <p>Is there a way to get the axes, with labels in the center of a ggplot2 plot, like a traditional graphing calculator? I've looked through the docs and there doesn't seem to be that functionality, but other plotting packages are not as graphically customizable as ggplot2. To clarify, I was looking to go from something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/qIwhu.png" alt="ggplot"></p>
  
  <p>To this:</p>
  
  <p><img src="https://i.stack.imgur.com/85WSK.png" alt="mathematica"></p>
  
  <p>The first plot is made with the following code:</p>
  
  <pre><code>dat = data.frame(x = 1, y =1)
  p = ggplot(data = dat, aes(x=x, y=y)) + geom_point(size = 5)
  p + xlim(-2,2) + ylim(-2,2)
  </code></pre>
  
  <p>The second plot is made with Mathematica. The main problem I am having is figuring out how to make the axis, with labels, go to the center (I can make the theme blank, etc., no problem). There seems to be no theme parameter you can edit to make this a quick fix.</p>