title: ggplot2 spacing of y values
body: <p>I'm trying to create a plot in ggplot2.  Here are the data, named problem_accept_df:</p>
  
  <pre><code>Order Application probscore
  1  Integrated 0.8333333
  1      Tabbed 0.7777778
  2  Integrated 0.8965517
  2      Tabbed 0.7777778
  3  Integrated 0.7931034
  3      Tabbed 0.7777778
  4  Integrated       0.7
  4      Tabbed 0.6538462
  5  Integrated 0.9285714
  5      Tabbed 0.8333333
  6  Integrated 0.9310345
  6      Tabbed 0.8148148
  7  Integrated 0.8571429
  7      Tabbed 0.8518519
  8  Integrated 0.9333333
  8      Tabbed 0.6923077
  9  Integrated 0.9310345
  9      Tabbed 0.8461538
  10  Integrated 0.9285714
  10      Tabbed       0.8
  </code></pre>
  
  <p>And here is the code to create the plot:</p>
  
  <pre><code>ggplot(problem_accept_df, aes(x=Order, y=probscore, color=Application,
  group=Application)) + 
  xlab('Order') +
  ylab('Problem scores') +
  geom_line(position=pd, size=2) +
  geom_point(position=pd, size=4) +
  labs(title='Acceptable proportion of problem scores')
  </code></pre>
  
  <p>The plot is created, but the y values are displayed on equally spaced tick marks even though the values are not equally spaced.  The plot also displays every individual y value instead of a range.  I've tried to change that (<code>scale_y_continuous(breaks=seq(0.5, 1, 0.1))</code>) but I get the error message <code>Error: Discrete value supplied to continuous scale</code> so the problem must be more basic.  I would appreciate any suggestions about what to do. </p>