title: Same scale of geom point size for two separate ggplot
body: <p>When we create two separate plot with ggplot, the scale (for the size of geom point for example) is independent.</p>
  <pre><code>library(ggplot)
  library(ggpubr)
  
  df1=data.frame(x=1:10,y=1:10,s=1:10)
  p1=ggplot(df1,aes(x,y,size=s))+geom_point()
  
  df2=data.frame(x=1:10,y=1:10,s=1:10*10)
  p2=ggplot(df2,aes(x,y,size=s))+geom_point()
  
  
  ggarrange(p1,p2)
  </code></pre>
  <p><a href="https://i.stack.imgur.com/M9PUY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/M9PUY.png" alt="enter image description here" /></a></p>
  <p>In this combined graph, we can see that the size of the points appeared to be the same, whereas the value is not the same. Is it possible to fix the scale for the two plots.</p>
  <p>One solution is to use <code>facet_wrap</code> after <code>rbind</code>ing</p>
  <pre><code>df1$group=1
  df2$group=2
  
  ggplot(rbind(df1,df2),aes(x,y,size=s))+
    geom_point()+
    facet_wrap(~as.factor(group))
  </code></pre>
  <p><a href="https://i.stack.imgur.com/l0Jdw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/l0Jdw.png" alt="enter image description here" /></a></p>
  <p><strong>But for some reason, I would not bind the datasets.</strong></p>