title: X-axis labels on top out of the plot area
body: <p>I'm plotting a correlation heatmap with x-axis on top by using <code>switch_axis_position</code>.
  The x-axis labels are somewhat long, so I want it to be rotated by using <code>angle=90</code> and align them by using <code>hjust=0</code>.
  But this makes the labels too far from the x-axis and even gets them out of the plot area.</p>
  
  <pre><code>library(gtable)
  library(cowplot)
  library(grid)
  
  heatmap&lt;-ggplot(data=meltedh, aes(x=variable, y=X, fill=value))+
    geom_tile(color="White")+
    ylab("")+xlab("")+
    scale_fill_gradient2(low="blue3", high="red3", mid="white", 
                        midpoint=0,limit=c(-1,1), space="Lab", breaks=c(-0.5,0,0.5),
                        name="Correlation Coefficient")+
    theme(legend.position="bottom", 
          axis.text.x=element_text(angle=90, hjust=0))
  heatmap
  ggdraw(switch_axis_position(heatmap,axis='x'))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/vMydv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vMydv.png" alt="enter image description here"></a>
  How can I make this pretty? Any help would be great. Thanks.</p>