title: Error with ggplot2
body: <p>I don't know what am I missing in the code?</p>
  
  <pre><code>set.seed(12345)
  require(ggplot2)
  AData &lt;- data.frame(Glabel=LETTERS[1:7], A=rnorm(7, mean = 0, sd = 1), B=rnorm(7, mean = 0, sd = 1))
  TData &lt;- data.frame(Tlabel=LETTERS[11:20], A=rnorm(10, mean = 0, sd = 1), B=rnorm(10, mean = 0, sd = 1))
  i &lt;- 2
  j &lt;- 3
  p &lt;- ggplot(data=AData, aes(AData[, i], AData[, j])) + geom_point() + theme_bw()
  p &lt;- p + geom_text(aes(data=AData, label=Glabel), size=3, vjust=1.25, colour="black")
  p &lt;- p + geom_segment(data = TData, aes(xend = TData[ ,i], yend=TData[ ,j]),
                    x=0, y=0, colour="black",
                    arrow=arrow(angle=25, length=unit(0.25, "cm")))
  p &lt;- p + geom_text(data=TData, aes(label=Tlabel), size=3, vjust=1.35, colour="black")
  </code></pre>
  
  <p>Last line of the code produces the error. Please point me out how to figure out this problem. Thanks in advance.</p>