title: defining minimum point size in ggplot2 - geom_point
body: <p>Let's say I have a lot of values around 0,1 and a few around 10. I have mapped them i.e., with:</p>
  
  <pre><code>geom_point(aes(size=value))
  </code></pre>
  
  <p>..which gives me an image like this:
  <img src="https://i.stack.imgur.com/HjVcj.png" alt="enter image description here"></p>
  
  <p>It is hard to see the very small points. So I was wondering if I could set the scaling frame for the dot sizes. With:</p>
  
  <pre><code>scale_size_area(max_size=8)
  </code></pre>
  
  <p>I can set the max size but not a min size. I could log10 my data resulting in almost no point size difference. It would be perfect to define a minimum size and a maximum leaving out a specified distribution (like it is possible with scale_colour_gradient for example).</p>