title: Adding points with line (similar to excel's line with markers chart) to barplot in ggplot
body: <p>Note: I haven't found any post related to my question and I'm new to stack overflow, sorry if this has been done before. <br>
  Consider the following plot:</p>
  <pre><code>data.frame(var = c(&quot;a&quot;,&quot;b&quot;, &quot;c&quot;), num = c(2,3,4)) %&gt;% 
    ggplot(aes(var, num)) + 
    geom_bar(stat = &quot;identity&quot;) + 
    geom_point() + 
    geom_line()
  </code></pre>
  <p>With this I am able to make a barplot with points at the middle of each barplot. However, adding <code>geom_line</code> results in the following error:</p>
  <blockquote>
  <p>geom_path: Each group consists of only one observation. Do you need to
  adjust the group aesthetic?</p>
  </blockquote>
  <p>I just want to make a line that joins each point in the barplot. How do I do so?</p>