title: Exclude zero values from a ggplot barplot?
body: <p>does anyone know if it is possible to exclude zero values from a barplot in ggplot?</p>
  
  <p>I have a dataset that contains proportions as follows:</p>
  
  <pre><code> X5employf       prop X5employff
  1   increase 0.02272727           
  2   increase 0.59090909          1
  3   increase 0.02272727   1  and 8
  4   increase 0.02272727          2
  5   increase 0.34090909          3
  6   increase 0.00000000          4
  7   increase 0.00000000          5
  8   increase 0.00000000          6
  9   increase 0.00000000    6 and 7
  10  increase 0.00000000   6 and 7 
  11  increase 0.00000000          7
  12  increase 0.00000000          8
  13  decrease 0.00000000           
  14  decrease 0.00000000          1
  15  decrease 0.00000000   1  and 8
  16  decrease 0.00000000          2
  17  decrease 0.00000000          3
  18  decrease 0.10000000          4
  19  decrease 0.50000000          5
  20  decrease 0.20000000          6
  21  decrease 0.00000000    6 and 7
  22  decrease 0.00000000   6 and 7 
  23  decrease 0.10000000          7
  24  decrease 0.10000000          8
  25      same 0.00000000           
  26      same 0.00000000          1
  27      same 0.00000000   1  and 8
  28      same 0.00000000          2
  29      same 0.00000000          3
  30      same 0.21052632          4
  31      same 0.31578947          5
  32      same 0.26315789          6
  33      same 0.15789474    6 and 7
  34      same 0.00000000   6 and 7 
  35      same 0.05263158          7
  36      same 0.00000000          8
  </code></pre>
  
  <p>as you can see in the 'prop' column there are a lot of zero values. I am producing a facetted bar plot with 'X5employf' column as the facet. But because of the zero values I end up with a lot of empty space on my plot(see below). Is there a way of forcing ggplot to not plot the zero values? Its not the case of dropping unused factors as these are not NA values but 0s. Any ideas??!</p>
  
  <p><img src="https://i.stack.imgur.com/PlreC.png" alt="example plot"></p>