title: No line in plot chart despite + geom_line()
body: <p>I've read documentation and I think that my code should be right, but still there is no line between the points in the output. What is wrong?</p>
  
  <p>The x'axis is discrete and y'axis is continuous. </p>
  
  <p>My code</p>
  
  <pre><code> point.sqrmPrice  &lt;- ggplot(overview.df, aes(x = areaSize, y = sqrmPrice)) + 
        geom_line() +
        geom_point() + 
        scale_y_continuous(breaks = c(seq(min(overview.df$sqrmPrice), max(overview.df$sqrmPrice), by = 10000) )) + 
        theme_bw()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/1SNPK.png" rel="noreferrer"><img src="https://i.stack.imgur.com/1SNPK.png" alt="enter image description here"></a></p>