title: Setting y axis breaks in ggplot
body: <p>I'm having difficulty setting the breaks in my code, I've tried adding breaks=seq(0, 100, by=20) but just can't seem to get it to work right. Essentially I want the Y axis to go from 0-100 with ticks every 20. </p>
  
  <pre><code>    YearlyCI &lt;- read.table(header=T, text='
    Station Year       CI        se
       M-25 2013 56.57098 1.4481561
       M-45 2013 32.39036 0.6567439
        X-2 2013 37.87488 0.7451653
       M-25 2008     74.5       2.4
       M-45 2008     41.6       1.1
       M-25 2004     82.2       1.9
       M-45 2004     60.6       1.0
       ')
  
  
  library(ggplot2)
  ggplot(YearlyCI, aes(x=Year, y=CI, colour=Station,group=Station)) +
    geom_errorbar(aes(ymin=CI-se, ymax=CI+se), colour="black", width=.2) +
    geom_line(size=.8) +
    geom_point(size=4, shape=18) +
    coord_cartesian(ylim = c(0, 100)) +
    xlab("Year") +
    ylab("Mean Condition Index") +
    labs(fill="") +
    theme_bw() +
      theme(legend.justification=c(1,1), legend.position=c(1,1)) 
  </code></pre>