title: r and ggplot2: plot boolean values for a series of days, each entry should get their own y position
body: <p>Consider the following dataframe which describes for 5 consecutive days if a certain behavior occured for a certain person. Later there will be 5 persons and 28 days, but this little example should be sufficient to show what I want to achieve.</p>
  
  <pre><code>persons &lt;- data.frame(
    person1 = c(TRUE, TRUE, FALSE, TRUE, TRUE),
    person2 =  c(FALSE, FALSE, TRUE, TRUE, TRUE),
    person3 =  c(TRUE, FALSE, TRUE, TRUE, TRUE),
    day  = c(1, 2, 3, 4, 5)
  )
  </code></pre>
  
  <p>I now want to use ggplot2 to plot this, so the number of the day is put on the x axis. Each of the three persons should get their own y axis position (i.e. person 1 on top, then person 2, and person 3 at the bottom) and get their own color. for each of the days if the value is TRUE, there should be a point filled in the persons's color, otherwise nothing. So for example for person 2, there should be points at X position 3, 4 and 5.</p>
  
  <p>If used smallest examples with ggplot2 before, but have only plotted numbers before. So how do I control the y axis position, so all measurements of person 2 are put in the same y axis position, and how do I control the filled points, so that they are only there if the value is true?</p>