title: Add vertical bar in expression to plot
body: <p>I'd like to add an expression to a plot, in which a conditional term appears, such as E(Y|X). Using for example:</p>
  
  <pre><code>plot(x=c(.5),ylim=c(0,1),xlim=c(0,2))
  text(x=1,y=.5,labels=expression(E(X|Y)),pos=1)
  </code></pre>
  
  <p>does not do it, but it produces E(|(X,Y)). Obviously I do not know how to get the vertical bar into the expression properly - can somebody help? Thanks.</p>