title: How to add two different magnitudes of point size in a ggplot bubbles chart?
body: <p>I just encountered such graph attached where two colors of geom_point are used (I believe it is made by ggplot2). Similarly, I would like to have dots of one color to range from size 1 to 5, and have another color for a series of dots for the range 10 to 50. I have however no clue on how to add two different ranges of point in one graph. </p>
  
  <p>At the basic step I have: </p>
  
  <pre><code>a &lt;- c(1,2,3,4,5)
  b &lt;- c(10,20,30,40,50)
  Species &lt;- factor(c("Species1","Species2","Species3","Species4","Species5"))
  bubba &lt;- data.frame(Sample1=a,Sample2=b,Species=Species)
  bubba$Species=factor(bubba$Species, levels=bubba$Species)
  xm=melt(bubba,id.vars = "Species", variable.name="Samples", value.name = "Size")
  str(xm)
  ggplot(xm,aes(x= Samples,y= fct_rev(Species)))+geom_point(aes(size=Size))+scale_size(range = range(xm$Size))+theme_bw()
  </code></pre>
  
  <p>Any would have clues where I should look into ? Thanks!</p>
  
  <p><a href="https://i.stack.imgur.com/yVUcK.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/yVUcK.png" alt="enter image description here"></a> </p>