title: Increase size of points ggplot
body: <p>I have two datasets:</p>
  
  <pre><code>mydata1 &lt;- data.frame(Class=letters[1:10], Magnitude = rnorm(10, 3, sd = 1),
                        pValue= abs(rnorm(10, 8, 5)), number= sample (10:50, 10))
  mydata2 &lt;- data.frame(Class=letters[1:10], Magnitude = rnorm(10, 2, sd = 0.5),
                        pValue= abs(rnorm(10, 3, 4)), number= sample (10:50, 10))
  </code></pre>
  
  <p>I am trying to make two graphs maintaining the same scale between them</p>
  
  <pre><code>ggplot(mydata1, aes(x=Magnitude, y=number, size=pValue, label=Class), guide=F) +
      geom_point() +
      scale_size_continuous(limits=c(0,16), breaks = c(0,2,6,10,16))
  ggplot(mydata2, aes(x=Magnitude, y=number, size=pValue, label=Class), guide=F) +
      geom_point() +
      scale_size_continuous(limits=c(0,16), breaks = c(0,2,6,10,16))
  </code></pre>
  
  <p>My simple question is, how do I increase (proportionally) the size of the points? They are too small on the graph. The argument <code>max_size</code> is not recognized within <code>scale_size_continuous</code>.</p>
  
  <p>And if I use</p>
  
  <pre><code>ggplot(mydata2, aes(x=Magnitude, y=number, size=pValue, label=Class), guide=F) +
      geom_point() +
      scale_size_continuous(limits=c(0,16), breaks = c(0,2,6,10,16)) +
      scale_size_area(max_size=8)
  </code></pre>
  
  <p>it overrides the <code>scale_size_continuous</code>.</p>
  
  <p>Any help is appreciated as I run out of options ...  </p>