title: axis.break and ggplot2 or gap.plot? plot may be too complex
body: <p>I created a plot with ggplot2. It's about milk protein content. I have two groups and 4 treatments. I want to show the interaction between group and treatment, means and errorbars. The protein content starts at 2.6%. Now my y-axis starts there without a gap, but my supervisor wants to have one. 
  I tried axis.break() of the plotrix library, but nothing happened. I tried to rebuild the graphic with gap.plot but I was not successful, but I must admit that I'm no R-hero.</p>
  
  <p>Here's the code for my graphic: </p>
  
  <pre><code>Protein&lt;-ggplot(data=D, aes(x=treat, y=Prot,group=group, shape=group))+
    geom_line(aes(linetype=group), size=1, position=position_dodge(0.2))+
    geom_point(size=3, position=position_dodge(0.2))+
    geom_errorbar(aes(ymin=Prot-Prot_SD,ymax=Prot+Prot_SD), width=.2,      
  position=position_dodge(0.2))+ 
    scale_shape_discrete(name='group\n', labels=c('1\n(n =   
  22,19,16,20)\n','2\n(n = 15,12,14,12)'))+
    scale_linetype_discrete(name="group\n", labels=c('control\n(n =   
  22,19,16,20)\n','free-contact\n(n = 15,12,14,12)'))+
    scale_x_discrete(labels=c('0', '1', '2', '3'))+
    labs(x='\ntreatment', y='protein content (%)\n')
  ProtStar&lt;-Protein+annotate("text", x=c(1,2,3,4), y=c(3.25,3.25,3.25,3.25),   
  label=c("Aa","Aa","Ab","Ba"), size=4)
  plot(ProtStar)
  </code></pre>
  
  <p>Unfortunately I do not have enough reputation to post images, but you might see from the code that the graphic is complex.</p>
  
  <p>It would be fantastic if you would have useful suggestions.
  Thanks a lot!</p>