title: how to plot proportion data with a bubble plot in R
body: <p>I have proportion data on the diet of a fish species from two separate years. I am struggling with how to get the bubble sizes to reflect that the range of possible values is from 0-1, but no value actually reaches 1. This is a plot I made in SigmaPlot that I would like to recreate in R. There are 12 different prey item categories. </p>
  
  <p><img src="https://i.stack.imgur.com/hx7Jw.png" alt="enter image description here"></p>
  
  <p>I have managed to create a plot in R but the sizes seem to be scaled to the largest proportion. Here is the code and reproduced plot.</p>
  
  <pre><code>library(reshape)
  library(ggplot2)
  
  Species &lt;- as.character(c(1:12))
  yr2016 &lt;- as.numeric(c(0.17, 0.011, 0.022, 0.003, 0.51, 0.1, 
                         0.01, 0.03, 0.004, 0.06, 0.07, 0.01))
  yr2017 &lt;- as.numeric(c(0.197, 0.005, 0.027, 0.01, 0.337, 0.157,
                         0.008, 0.038, 0.017, 0.17, 0.032, 0.002))
  data &lt;- as.data.frame(cbind(Species, yr2016, yr2017))
  data$yr2016 &lt;- as.numeric(as.character(data$yr2016))
  data$yr2017 &lt;- as.numeric(as.character(data$yr2017))
  data2 &lt;- melt(data)
  
  ggplot(data2,
         aes(x = variable, y = factor(Species, levels = unique(Species))))+
    geom_point(aes(size = value))+
    labs(y = "Prey Items", x = "Year")+
    theme_classic() +
    scale_size_area()
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/uatpI.jpg" alt="enter image description here"></p>