title: Set y axis label position ggplot2
body: <p>I am looking for graphic help using ggplot2.
  I am plotting to different variables (A and B) against the same variable C. Variable A has values from -20 to 20, whereas variable B has values from -2 to 2. When using ggplot2, the y-axis-label is further away from the axis line for variable A than for variable B, as 20 takes more space than 2 and the label has the same distance to the numbers. </p>
  
  <p>I would like to have the same distance for both. Is there a possibility of defining the distance between the axis label and the line?</p>
  
  <p>I have tried working with theme(axis.title.y = element_text(vjust=) ) but this makes it very hard to set the distance equally.</p>
  
  <p>I also tried adding "\n" after my yaxis title, as suggested here (<a href="https://groups.google.com/forum/#!topic/ggplot2/mK9DR3dKIBU" rel="nofollow">https://groups.google.com/forum/#!topic/ggplot2/mK9DR3dKIBU</a>) but this does not resolve my problem either. </p>
  
  <p>An example using the PlantGrowth data:</p>
  
  <pre><code>  bp &lt;- ggplot(PlantGrowth, aes(x=group, y=weight)) +
          geom_boxplot()+
          theme_classic(base_size=16) +
          ylim(c(3,7))+
          coord_fixed(ratio=(3)/(4))
  
  bp1000 &lt;- ggplot(PlantGrowth, aes(x=group, y=weight*1000)) +
          geom_boxplot()+
          theme_classic(base_size=16) +
          ylim(c(3000,7000))+
          coord_fixed(ratio=(3)/(4000))
  </code></pre>
  
  <p>you will see that the label of the y axis ("weight") is further away from the axis for bp1000 than for bp, even if with coord_fixed() it is quite easy to keep the plotting area the same. </p>
  
  <p>How can I define that the distance for the ylabel for bp should be the same (i.e. longer) as for bp1000. </p>