title: How to plot one variable in ggplot?
body: <p>I'm searching but still can't find an answer to a quite simple question - how can we produce a simple dot plot of one variable with ggplot2 in R? </p>
  
  <p>with <code>plot</code> command this is very simple:</p>
  
  <pre><code>plot(iris$Sepal.Length, type='p')
  </code></pre>
  
  <p>But when I'm trying to pass one variable to qplot and specifying geom="point", I'm getting an error "Error in UseMethod("scale_dimension")". </p>
  
  <p><img src="https://i.stack.imgur.com/66LrH.png" alt="Simple one-variable plot"></p>
  
  <p>How can we make a plot like this but with ggplot2?</p>