title: Changing the range of sizes used in a bubble plot
body: <p>I'm using R to create a competitive map of strategic groups in the industry I'm researching. The number of outlets is along the x-axis, Sales is the y-axis as well as the size of the bubble.  Code used:</p>
  
  <pre><code>qplot(data = supermarket, x = outlets, y = sales, size = sales, color = retailer)   
  </code></pre>
  
  <p>However, I need to increase the overall size of the bubbles as it is too unclear at the moment. Please see below for an example.</p>
  
  <p><img src="https://i.imgur.com/x6WTT.png" alt="Graph"></p>
  
  <p>What I need is to have the bubbles keep their size relative to sales but become larger overall to increase the visibility.</p>