title: How to add a title to legend scale using levelplot in R?
body: <p>I would like to add a title to my legend for this plot:</p>
  
  <pre><code>     library(lattice)
       x = 1:10
       y = rep(x,rep(10,10))
       x = rep(x,rep(10))
       z = x+y  
       levelplot(z~x*y,  
                 colorkey = list(labels = list(cex=1,font=2,col="brown"), height=1, width=1.4),
                 main = list('b',side=1,line=0.5))
  </code></pre>
  
  <p>Which produces:</p>
  
  <p><img src="https://i.stack.imgur.com/VfHZD.png" alt="enter image description here"></p>