title: geom_text with dodged barplot
body: <p>I try to add text as in <a href="https://stackoverflow.com/questions/6017460/ggplot-geom-text-with-dodged-barplot">Position geom_text on dodged barplot</a>
  But its not work with my simple data</p>
  
  <pre><code>data=data.frame(s=c(10,13,17,8),
                  pr=c("a","b","a","b"),
                  m=c(rep(as.Date('01.01.2015','%d.%m.%Y'),2), rep(as.Date('01.02.2015','%d.%m.%Y'),2)))
  </code></pre>
  
  <p>And ggplot </p>
  
  <pre><code>ggplot(data = data 
         ,aes(x = m, y = s,fill=pr ,ymax = max(s)*1.1))+
    geom_bar(position = "dodge",stat="identity")+
    geom_text(aes(y=s/2,label=paste(round(s,3),"%")),position = position_dodge(width=1))+
    scale_x_date(labels = date_format("%m/%y"),breaks = date_breaks("months"))
  </code></pre>
  
  <p>i get</p>
  
  <p><a href="https://i.stack.imgur.com/vZjTf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vZjTf.png" alt="enter image description here"></a></p>
  
  <p>How to add text in right position( in the middle of each bar)?
  Thanks!</p>