title: R: combine barplot and lineplot; line-dots and ticks on the x-axis not aligned to barplot
body: <p>I want to plot two outcomes of a behavioral psychological experiment in one plot: performance (as measured by % of correct answers) through a marplot and reaction times (in ms) through a line plot.</p>
  
  <p>I've figured everything out except one thing: the ticks on the x-axis and the dots in the line plot don't align with the center of the bars. Someone suggested to save the barplot as an object and then use "at=" which works for the ticks on the x-axis but not for the dots in the line plot. I also wasn't able to make it work by using the "lines" function since the scales are different (.7-1.0 on the left for the barplot and 400-900 on the right for the line plot).</p>
  
  <pre><code>par(mar=c(6, 4, 4, 4))
  m&lt;-barplot(c(0.87,0.83,0.79),ylim=c(0.7,1),xpd=FALSE,ylab="% correct")
  axis(1,at=m,labels=c("cond. A", "cond. B", "cond. C"))
  par(new=T)
  plot(c(720, 800, 830), pch=15, ,ylim=c(400,900), xlab="", ylab="",      
        axes=F, type="b")
  mtext("reaction time [ms]",side=4,line=2.5)
  axis(4, ylim=c(400,900))
  </code></pre>
  
  <p>Thank you for any kind of help</p>