title: scale_x_discrete not showing data some data and hiding another
body: <p>I want to plot a graph showing data by fiscal year. The problem I have is that <strong>ggplot is showing a point that does not exist in the data frame containing the information, and not painting another that really exists</strong>. Could you please masters of ggplot help me? Thank you very much!!</p>
  
  <p>The code is:</p>
  
  <pre><code>    plot = ggplot(data = headcountPerMonth,
                aes(x = Month.Number, 
                    y = Headcount, 
                    group = Fiscal.Year, 
                    colour = Fiscal.Year)) +
         geom_line() +    
         geom_point() +  
         labs(colour = "Fiscal year") +
         scale_x_discrete(
           name = "Month", 
           labels = headcountPerMonth$Month.Name
         ) +
         scale_y_continuous(name = "Headcount");
      print(plot);
  </code></pre>
  
  <p>The plot is the next one. As you can see there is <strong>a value Month = March, Fiscal.Year = 2012, but not on Month = June, Fiscal.Year = 2012</strong>.</p>
  
  <p><img src="https://i.stack.imgur.com/GXnuY.png" alt="enter image description here"></p>
  
  <p>The data from the plot is the next one. As you can see <strong>there is no value Month = March, Fiscal.Year = 2012, but exists on Month = June, Fiscal.Year = 2012</strong>.</p>
  
  <pre><code>        Month Headcount Fiscal.Year Month.Number Month.Name
  1  2010-04-01        48        2010            4        abr
  2  2010-05-01        49        2010            5        may
  3  2010-06-01        52        2010            6        jun
  4  2010-07-01        51        2010            7        jul
  5  2010-08-01        51        2010            8        ago
  6  2010-09-01        51        2010            9        sep
  7  2010-10-01        52        2010           10        oct
  8  2010-11-01        54        2010           11        nov
  9  2010-12-01        54        2010           12        dic
  10 2011-01-01        56        2010            1        ene
  11 2011-02-01        56        2010            2        feb
  12 2011-03-01        61        2010            3        mar
  13 2011-04-01        61        2011            4        abr
  14 2011-05-01        59        2011            5        may
  15 2011-06-01        59        2011            6        jun
  16 2011-07-01        61        2011            7        jul
  17 2011-08-01        59        2011            8        ago
  18 2011-09-01        58        2011            9        sep
  19 2011-10-01        59        2011           10        oct
  20 2011-11-01        65        2011           11        nov
  21 2011-12-01        68        2011           12        dic
  22 2012-01-01        72        2011            1        ene
  23 2012-02-01        72        2011            2        feb
  24 2012-03-01        72        2011            3        mar
  25 2012-04-01        77        2012            4        abr
  26 2012-05-01        77        2012            5        may
  27 2012-06-01        80        2012            6        jun
  28 2012-07-01        80        2012            7        jul
  29 2012-08-01        77        2012            8        ago
  30 2012-09-01        81        2012            9        sep
  31 2012-10-01        86        2012           10        oct
  32 2012-11-01        86        2012           11        nov
  33 2012-12-01        85        2012           12        dic
  34 2013-01-01        88        2012            1        ene
  35 2013-02-01        86        2012            2        feb
  </code></pre>
  
  <p>Thanks in advance for your help.</p>