title: How to make geom_text() parallel to geom_segment() in a log-lin scale?
body: <p>One needs to annotate a line in a log-lin plot. How do you make the text string (here "0000000000") parallel to the line it is annotating?</p>
  
  <pre><code>require(ggplot2)
  require(scales)
  x=c(1:10)
  y=2^x
  data_line &lt;- data.frame(x=3,xend=8,y=2^8,yend=2^9)
  line &lt;- geom_segment(data=data_line,aes(x=x,xend=xend,y=y,yend=yend),color="blue")
  angle= atan((data_line$yend - data_line$y) / (data_line$xend - data_line$x))*(180/pi)
  text &lt;- annotate("text",x=data_line$x,y=data_line$y,label="0000000000",angle=angle)
  qplot(x=x,y=y,geom="line") + line + text + scale_y_log10()
  </code></pre>