title: grid.arrange(): arrange 3 plots neatly
body: <p>I want to arrange 3 square ggplots showing one of them bigger and the other two smaller alongside with the first one. </p>
  
  <p>Here is my attempt:</p>
  
  <pre><code>gg1 &lt;- ggplot(mtcars,aes(x=hp,y=mpg))+
          geom_point(aes(color=factor(cyl)),alpha=.5)+
          stat_smooth(method='lm', se=F, color='red')+
          ggtitle('plot 1')+
          theme_bw()+
          theme(aspect.ratio=1,
                legend.position = c(1, 1), 
                legend.justification = c(1,1), 
                legend.background = element_rect(colour = NA, fill = NA))
  
  
  gg2 &lt;- ggplot(mtcars)+
          geom_density(aes(x=hp, color=factor(cyl)))+
          ggtitle('plot 2')+
          theme_bw()+
          theme(aspect.ratio=1,
                legend.position = c(1, 1), 
                legend.justification = c(1,1), 
                legend.background = element_rect(colour = NA, fill = NA))
  
  
  gg3 &lt;- ggplot(mtcars)+
          geom_density(aes(x=mpg, color=factor(cyl)))+
          ggtitle('plot 3')+
          theme_bw()+
          theme(aspect.ratio=1,
                legend.position = c(1, 1), 
                legend.justification = c(1,1), 
                legend.background = element_rect(colour = NA, fill = NA))
  
  grid.arrange(arrangeGrob(gg1), 
               arrangeGrob(gg2,gg3, ncol=1), 
               ncol=2, widths=c(1,1))
  </code></pre>
  
  <p>Basically, I want the top border of the small plot2 to be level with the top border of the big plot1, and the bottom border of plot3 to be level with the bottom border of plot1. Also ggtitle1 should be level with ggtitle 2.</p>
  
  <p>When I save my triple plot (even keeping the desired aspect ratio)</p>
  
  <pre><code>png(file = 'test.png',width=900,height=600)
  grid.arrange(arrangeGrob(gg1), 
               arrangeGrob(gg2,gg3, ncol=1), 
               ncol=2, widths=c(1,1))
  dev.off()
  </code></pre>
  
  <p>I get something like this </p>
  
  <p><a href="https://i.stack.imgur.com/ifPen.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ifPen.png" alt="enter image description here"></a></p>
  
  <p>Any ideas on how to manage the neat arrangement?</p>