title: Changing Y-axis breaks in ggplot2
body: <p>I have this code to give the graph shown below:</p>
  
  <pre><code>d=ggplot(df, aes(x=Year, y=NAO_Index, width=.8)) +
  + geom_bar(stat="identity", aes(fill=NAO_Index&gt;0), position='identity', col = 'transparent') +
  + theme_bw() + scale_fill_manual(values=c("royalblue", "firebrick3"), name="NAO Oscillation", labels=c("Negative", "Positive"), guide=guide_legend(reverse=TRUE)) +
  theme(legend.position=c(0.06, 0.92)) + 
  + theme(axis.title.x=element_text(vjust=-0.2)) +
  + geom_line(data=dfmoveav, aes(x=Year ,y=moveav)) +
  + ylab("NAO Index") +
  + ggtitle("NAO Index between 1860 and 2050") +
  + scale_x_continuous(breaks=c(seq(1860,2050,10))) +
  + scale_y_continuous(breaks=c(seq(-3.5,3.5,0.5)))
  </code></pre>
  
  <p>I am only really concerned with the last line. In the graph the y-axis only goes from -3 to 2.5. How do I get it from -3.5 to 3.5 so it is even?</p>
  
  <p>I'm sure I am making a simple error but cannot figure it out!</p>
  
  <p><img src="https://i.stack.imgur.com/4wwf2.jpg" alt="enter image description here">Many thanks in advance.</p>