title: Remove white space in ggarrange, ggplot2
body: <p>Say I have three SQUARE plots p1 p2 p3 made from the <code>ggplot2</code> package. I applied <code>ggarrange</code> command under <code>ggpubr</code> package to make a 1*3 plot after that. Here are the commands:</p>
  
  <pre><code>library(ggplot2)
  library(ggpubr)
  library(gridExtra)
  data &lt;- data.frame(matrix(seq(1, 30, 1), 2))
  
  for(i in 1:5){
    plot1 &lt;- ggplot(data = data, aes(y = data[, (i*3-2)])) + 
        theme(aspect.ratio = 1)
    plot2 &lt;- ggplot(data = data, aes(y = data[, (i*3-1)])) + 
        theme(aspect.ratio = 1)
    plot3 &lt;- ggplot(data = data, aes(y = data[, (i*3)])) + 
        theme(aspect.ratio = 1)
    p &lt;- ggarrange(plot1, plot2, plot3,
                   ncol = 3, common.legend = TRUE, legend = "bottom")
    grid.arrange(p, top = paste(colnames(data)[i]), heights = c(1, 1))
  }
  </code></pre>
  
  <p>The rmarkdown output (below) shows a large white space below the arranged plots:</p>
  
  <p><a href="https://i.stack.imgur.com/MG1UJ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MG1UJ.png" alt="enter image description here"></a></p>
  
  <p>Is there any way to remove it? What I thought is to change the default size of canvas..</p>