title: Variable binwith in geom_histogram()
body: <p>I like to set up different binwidths in ggplot2.</p>
  
  <p>As an example I use the dataset</p>
  
  <pre><code>library(Stat2Data)
  data("YouthRisk2007")
  </code></pre>
  
  <pre><code>head(YouthRisk2007)
    ride.alc.driver female grade age4 smoke DriverLicense
  1               1      1    10   15     1             0
  2               1      1    10   18     1             1
  3               1     NA    NA   NA    NA            NA
  4               0      0    11   17     0             1
  5               0      0    11   17     0             1
  6               0      0    11   17     1             1
  </code></pre>
  
  <p>With </p>
  
  <pre><code>library(dplyr)
  library(ggplot2)
  
  YouthRisk2007 %&gt;% 
      ggplot(aes(age4)) +
        geom_histogram(binwidth = 1)
  </code></pre>
  
  <p>you generate a histogram for every year.</p>
  
  <p>Now I like to set up different binwidth (14-15 year, 16-17 year, 18 years [width of the classes]) so that the area is proportional to the frequency (not just the hight of the bin).
  The binwidth should vary visually, not just for counting the frequency.</p>
  
  <p>My first idea was to set up the binwidth as a vector <code>binwidth = c(2,3)</code> but this is not allowed.</p>
  
  <p>Is there a way to do this?</p>