title: Bar plot with facets and same bar size (binwidth) with option to shrink the panel size
body: <p>I want to compare data in a facet-alike manner using a <strong>bar plot</strong>, but missing data causes the bar "widths" to be different:</p>
  
  <p><a href="https://i.stack.imgur.com/djOUT.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/djOUT.png" alt="enter image description here"></a></p>
  
  <p>How can I</p>
  
  <ol>
  <li>ensure the same bar size ("width") and</li>
  <li>[nice to have] shrink the panel size of each facet to the really required size?</li>
  </ol>
  
  <p>PS: I do not want to show empty data as "zero-bar" to waste no space.</p>
  
  <pre><code>library(ggplot2)
  data &lt;- data.frame(product = c("Fish", "Chips", "Baguette"),
                     store = c("London", "London", "Paris"),
                     customer.satisfaction = c(0.9, 0.95, 0.8),
                     stringsAsFactors = TRUE)
  data
  
  ggplot(data, aes(x = product, y = customer.satisfaction)) +
  geom_bar(stat = "identity", width = 0.9) +
  coord_flip() +
  facet_wrap( ~ store, ncol = 1, scales = "free_y")
  </code></pre>